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Bright LIGHTS, Big Science A Facilitator's Guide to Light Our Vision Canadians recognize that 1 Science is intrinsic to their lives and acknowledge the fundamental importance of a quality Science education to prepare young people for our rapidly changing world. Our Mission Let’s Talk Science is striving to improve Science literacy through innovative educational programs, research and advocacy. We exist to motivate and empower young Canadians through Science education. 1 Our Science includes life and physical sciences, technology, engineering and mathematics. Let’s Talk Science National Office 1584 North Routledge Park London, Ontario, Canada N6H 5L6 Tel: 519-474-4081 Fax: 519-474-4085 Email: [email protected] www.letstalkscience.ca Charitable Number: BN88540 0846 RR0001 www.letstalkscience.ca Developed by Laura Brown, Shauna McAdam, Kim Mustard-Fenton and Maria Varju For ©2003 Let's Talk Science National Cornerstone Supporters: National Founding *Registered trademark of Imperial Oil Limited. Used under License. To make a tax-deductible donation to improve Science literacy in Canada, please call Toll Free: 1-866-352-3060 or 519-474-4084 or visit our web site: www.letstalkscience.ca All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from LET'S TALK SCIENCE. Page 2 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science A. Description of Workshop Overview of Workshop Grade for Workshop/ Appropriate Age This activity is designed for use in Grade 3-4 classrooms or with children ages 6-10. Where does light come from? How does it travel between a source and our eyes? Learn about light and how it is transmitted, reflected and refracted by materials in our environment. Use this knowledge to make a take home kaleidoscope. Overall Objectives Science Topics Sources of light Transparent/ translucent/ opaque Shadows Reflection Refraction www.letstalkscience.ca To identify natural and artificial sources of light To look at ways we use light To look at the classification of materials as transparent, translucent or opaque To identify that opaque objects cast shadows. Page 3 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science B. How to Run This Workshop Physical Requirements Desks should be arranged into 6 groups. This workshop requires the use of an overhead projector. Materials and Set-Up Students will travel to 3 activity stations in the classroom. There will be 6 stations in total - 2 of each activity. Students will work in groups of 4 or 5 at the stations and rotate for activities 1, 2 and 3. Activity 4 will be done together. Every student will make a take-home kaleidoscope of their own. Note: For more detail, see Kit List. Each activity gives the list of supplies for only 1 station. Introduction Pictures of artificial and natural light sources Term cards: translucent, opaque, transparent, reflection and refraction. Station tent cards Activity #1 Absorption Acetate Screen Tissue paper Cardboard Non glare Plexiglass Aluminum Foil Plastic bag White paper 8 - 4”x6” frames made from cardboard or plastic cardboard 5-6 laminated www.letstalkscience.ca Activity #2 Mirror Maze 5 – Locker Mirrors Activity #3 Refraction 1 Flashlight (small enough to fit in paper towel tube) Activity #4 Kaleidoscope *Cardstock 5 Plastic Concave lens cardboard walls (1 big, 4 small) *Acetate pieces 30 large 30 small 10 Large sized Hair pick/comb **30 Permanent Page 4 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science LTS logos 2 Flashlights markers 3 Petri dishes *Straight pins with round heads, 30/class Fish picture on Plasticine to Picture of light Glass or baby food *Reflective mylar acetate support shadow bulb jar or clear plastic pieces 30/class (or, acetate, coloured objects jar acetate, frosted and (optional) opaque material) *Water 4 Shadow Pictures of Plasticine (1 block) *Tape, 12 rolls pictures, periscopes and laminated submarines *Food colouring Shadow objects: 2 Medium *Food colouring *Glue stick, 12 tubes dull scissors, sized combs, fold clip, flashlights plastic spiders, tape dispensers *Cornstarch Plasticine for *Water *Rubbing flashlight alcohol(optional) stand (optional) *Plastic spoon White placemat Plastic cardboard 22” x 14” Hot Wheels™ cars (2) Locker mirror Bouncy ball clips Mat with pre- Paper towel or printed maze toilet paper tube 3 Magnifying glasses Little pictures Cheap lenses mini-binoculars, mini-microscope (optional) 2 Refraction viewers *Scrap paper (optional) *Consumable items **Eventually needs replacing www.letstalkscience.ca Page 5 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Timing of Activity Part of Workshop: General Introduction Introduction to Topic and Explanation of Activities Activity #1a, 1b Activity #2a, 2b Activity #3a, 3b Activity #4-Take home Wrap-Up Suggested Timing: 5 min. 20 min. Cumulative Timing: 5 min. 25 min. 15 min. 15 min. 15 min. 20 min 10 min. 40 min. 55 min. 70 min. 90 min 100 min. C. Introduction to Topic Objectives of Introduction To introduce light as a form of energy and that it is produced by or comes from a natural or artificial source. Suggested Discussion, Q & A Today, we are going to be talking about light. All light comes from or is produced by a source. Can you name some sources of light? (As the students brainstorm, put up the pictures of the sources or write the words on the board). (Then, separate the pictures or words into the categories of Natural Sources or Artificial Sources). Natural Sources www.letstalkscience.ca Page 6 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Sun, stars, lightning, fire/burning objects, bioluminescence occurring in fireflies (or glowworms), sea creatures (protozoa, comb jellyfish, sea pen, parchment tube worm, deep-sea squid, lantern fish, angler fish, bacteria), orange milkcap mushroom, etc. * The moon may be mentioned here, but the moon shines because the sun’s light is bouncing or reflecting off its surface. Actually, people, plants and houses all reflect light. Artificial Sources Lamp, glow-stick, candle, campfire, oil lamps, gas lamps, bulbs, fluorescent tubes, neon lights, Indiglo™ watches, toys, lasers, etc. What is the difference between a natural and an artificial source of light? Natural is something that occurs in nature. Very hot objects can produce light. That is how light is produced by the sun and why we see a nice yellow glow from burning wood. The main source of natural light on Earth is the sun. Artificial is people-produced (or man-made). The first artificial source of light in pre-historic times was the campfire, as it was made by people to give light and heat. Electricity is now our main source of artificial light. CHOICE: Skip over this part if it does not relate to your curriculum or give a few examples before asking the question. We use light for many different things. Can you think of some of the important jobs that light has? Warn us of danger (i.e. fire truck, police cars, ambulance lights), alert us (i.e. crosswalk lights, exit lights, airport runway lights), safety (i.e. traffic lights, stove lights), allows us to see in the dark (i.e. flashlights, street lights, lights at the bottom of swimming pools, camera flash), information (advertising), beauty or entertainment (laser light shows), etc. Do you know what light is? www.letstalkscience.ca Page 7 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Light is a type of energy that spreads out from a source in all directions, like the spokes of a bicycle wheel. Light travels at a very high speed and light travels in straight lines. Everything we look at is seen because of light bouncing off objects and then into our eyes. We are now going to learn what happens to light as it travels from a source on its way to our eye. BRIGHT IDEA: Some interesting facts about light can be interjected into the program at appropriate places such as: light from the sun, 150 million kilometers away, reaches us in only 8.3 minutes light reflected from the moon takes about 1.3 seconds to reach us light travels about one million times faster than sound travels in air light could travel around the planet Earth 7.5 times in one second the speed of light is about one billion kilometers per hour D. Activities ACTIVITY #1a:TRANSMISSION OF LIGHT (10 min.) Oral instructions – pictorial instructions on worksheet Objective of Activity To understand the classification of materials as transparent, translucent or opaque. Suggested Instructions, Q & A Transmission of Light Demo CHOICE 1: If you have access to an overhead projector use the Page 8 of 41 following Q&A, if not use a In-class coloured fish,Bright acetates opaque workshops, LIGHTS,and Big Science material instead, suggested Q&A to follow. ©2003 Let’s Talk Science www.letstalkscience.ca www.letstalkscience.ca Page 9 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science CHOICE 1: Overhead Projector To help explain the concept of transparent, translucent and opaque, the facilitator will use an overhead projector, an acetate picture of a fish and 3 petri dishes – one with water, one with water and a lot of cornstarch, and one with water and a little cornstarch. The first thing we are going to learn about light is that it can pass through many forms of matter. I’m going to use the overhead projector to help me demonstrate this property of light. What is the source of light in this overhead? A light bulb. (Put the fish on the overhead, cover the fish with a Petri dish and add a bit of water to the dish.) Can we see the fish through the water? Yes. Why? The water is clear. Yes, when we are talking about light, we say that the water is transparent. What does a transparent material allow the light to do? A transparent material lets all the light through. What are some things in the classroom that are transparent? Air, glass and windows, etc… (Put the text card with the word transparent on the board.) (Add a drop or 2 of food colouring to the water in the petri dish.) What happens when we add food colouring to the water? Can we still see the fish? Yes, the water is still transparent, but coloured. Can you think of some places we use coloured transparent materials everyday? Sunglasses, visors, anti-glare screen on a computer, report covers, traffic lights, car windshields, holiday lights, sun catchers, stained glass, etc… Now, what will happen when we add cornstarch to the water? (Mix some corn starch and water in another petri dish and place it over the fish on the overhead.) You cannot see the fish. The fish is not visible any more. The water has become opaque. Why can we no longer see the fish? The water does not let the light through – it does not transmit the light. The fish is still there, but we cannot see it because the water is opaque. www.letstalkscience.ca Page 10 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science So what does opaque mean? Something that is opaque doesn't let light through. What are some things in the room that are opaque? Walls, curtains, tables, chairs, etc. (Put the text card with the word opaque on the board.) Now, what will happen when we only add a little bit of cornstarch to the water? (Mix a very small amount of the cornstarch into a petri dish.) It's a little fuzzy. This is translucent. Translucent means that some light travels through it. What are some objects in the room that are translucent? Light covers, frosted glass, report covers Light can pass through some types of materials. The amount of light that passes through depends on the kind of materials. That material can be transparent, opaque or translucent. CHOICE 2: If you do NOT have access to an overhead projector use the following Q&A. To help explain the concept of transparent, translucent and opaque the facilitator will use an acetate picture of a fish, a clear acetate, a frosted acetate and a piece of cardstock. The first thing we are going to learn about light is that it can pass through many forms of matter (Hold up the fish, cover the fish with the clear acetate.) Can we see the fish through the acetate? Yes. Why? The acetate is clear. Yes, when we are talking about light, we say that the acetate is transparent. What does a transparent material allow the light to do? A transparent material lets all the light through. What are some things in the classroom that are transparent? Air, glass and windows, etc…(Put the text card with the word transparent on the board.) www.letstalkscience.ca Page 11 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science (Cover the fish with the coloured acetate.) What happens when we add coloured acetate? Can we still see the fish? Yes, the acetate is still transparent, but coloured. Can you think of some places we use coloured transparent materials everyday? Sunglasses, visors, anti-glare screen on a computer, report covers, traffic lights, car windshields, holiday lights, sun catchers, stained glass, etc… Now, what will happen when we put cardstock over the fish? You cannot see the fish. The fish is not visible any more. The cardstock is opaque. Why can we no longer see the fish? The cardstock does not let the light through – it does not transmit the light. The fish is still there, but we cannot see it because the cardstock is opaque. So what does opaque mean? Something that is opaque doesn't let light through. What are some things in the room that are opaque? Walls, curtains, tables, chairs, etc. (Put the text card with the word opaque on the board.) Now, what will happen when we put a frosted acetate over the fish? It's a little fuzzy. This is translucent. Translucent means that some light travels through it. What are some objects in the room that are translucent? Light covers, frosted glass, report covers Light can pass through some types of materials. The amount of light that passes through depends on the kind of materials. That material can be transparent, opaque or translucent. CHOICE: You can explain Station #1a at this point or explain all of the stations at the end of the introduction. www.letstalkscience.ca Page 12 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Station Explanation At this first station you will be making predictions about which materials are transparent, translucent and opaque. Examine each material and record your prediction on the worksheet (show the worksheet). Then test each material and see if the picture of our logo is visible through the materials. This is your test result. Record these results on your worksheet. What materials are translucent, transparent or opaque? The students will make predictions and test the following materials. The materials will be mounted in 4”x 6” frames. Acetate (overhead transparency) Window screening Tissue paper Cardboard Plexiglass Plastic shopping bag Aluminum Foil White paper ACTIVITY #1b: SHADOWS (5 min.) Oral instructions Objectives of Activity: To understand how a shadow is created and discover how light direction affects the location, size and shape of shadows Suggested Instructions, Q & A You will be given pictures of shadows made with various household objects. You will also be given a bag of objects and a flashlight. By positioning the light and the objects recreate the shadow pictures. What happens when light shines on an opaque object? You get a shadow. Light does not go through the object. www.letstalkscience.ca Page 13 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Station Explanation DELIVERY HINT: It may be useful to tell students that when recreating the shadow, try to recreate the angle and size of the shadow. Place an object upright on the X beside the picture of a shadow. Use a piece of plasticine to hold the object in an upright position. Using a flashlight, move the flashlight around the object to recreate the shadow picture. ACTIVITY #2a: REFLECTION – MIRROR MAZE (10 min.) Oral instructions Objectives of Activity To show that light travels in straight lines. To see that light bounces off reflective objects. Suggested Instructions, Q & A We have already learned one important thing about light, and that is that it can travel through some materials and not others. The next thing that we are going to talk about is how light reflects off of certain objects. What is reflection? When light strikes a mirror it bounces off. This is called reflection of light. When you see the image of your face in a mirror, you are seeing the reflection of light from your face. Where do you see your reflection? Mirrors, glass, shiny metals. A) Reflection Demo #1 Have a student volunteer stand at the front of the class. The volunteer must keep their eyes facing straight ahead. How can they use a mirror to www.letstalkscience.ca Page 14 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science see their feet? They might say that they could hold the mirror in front of them. Have them try to hold the mirror perpendicular to the floor so that they still can’t see their feet. What do they need to do now to see their feet? They need to angle the mirror. Or they need to move the mirror downwards towards their feet. Have them track the path of light from the source to their feet up to the mirror and into their eyes. The light was bouncing off the mirror at an angle. BRIGHT IDEA: Have the student stand sideways so their classmates can see the angle of the mirror. Use the ball to demonstrate how light bounces off a mirror. When the student held the mirror perpendicular to the floor the light bounced straight back so all they could see was their eyes (or maybe their face and what is directly behind them). Bounce the ball directly down. The ball should come straight back up. When the student tilted the mirror the light hit it at an angle and then bounced back at an angle. Light reflects from a mirror at the same angle as it arrives. Normal angle of reflection angle of incidence Angle of incidence is equal to the angle of reflection. www.letstalkscience.ca Page 15 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Station Explanation At the reflection station you will set up the maze on the designated mat. Lines are pre-drawn indicating where the maze walls, flashlight and light bulb picture should be placed. Working as a team, you will need to arrange the mirrors throughout the maze so that when you shine the light into the maze the light reflects off of the mirrors and shines on the picture of the light bulb at the end. DELIVERY HINT: Set this station up ahead of time so the students can see an example. Tape the maze mat to the table. BRIGHT IDEA: If the students finish early. Have them rearrange the maze adding more walls and more mirrors ACTIVITY #2b: MIRROR WRITING (5 min.) Task card Oral instructions Objectives of Activity To see that the image seen in the mirror is a flip of the original object. Station Explanation Write your name on the worksheet so that when you look at it in a mirror it appears correct. Mirror www.letstalkscience.ca Page 16 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science ACTIVITY #3a: REFRACTION – BENDING LIGHT(15 min.) Oral instructions Objectives of Activity To demonstrate that refraction is the bending of light as it passes from one transparent material to another. To observe refraction using simple lenses and devices. Suggested Instructions, Q & A We have already learned two important things about light – it can go through some different materials and it can be reflected off of smooth surfaces. A) Toy Car Demo There is a third thing that happens to light as it travels. Let me demonstrate using these two toy cars and two different road surfaces. Imagine that each car is a ray of light energy travelling very fast in a straight line. (The speed of light is about 300 000 km/s.) The material that light travels through can affect its speed. Which car will travel faster, the one going on the smooth surface or the one on the rough surface? The car on the smooth surface. DELIVERY HINT: Don’t use a steep incline when releasing the car. (Have yourself or 2 volunteers release the cars at the same time. The “ramp” should be on a slight angle so the entire class can see.) www.letstalkscience.ca Page 17 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science On the smooth road, there was less resistance so that car traveled faster. On the rough road, there was more resistance so this car traveled at a slower speed. The same thing happens with light. What will happen if one car, one ray of light, travels from the smooth surface to the rough surface? The car will slow down when it hits the rough surface. (Move one car so that it travels in a straight line from the smooth surface to the rough surface.) What happens when you ride your bike from the road straight onto the grass or into sand? You slow down, change speed That is what is happening to light in this case. Now, what will happen to the car as it travels on an angle from the smooth surface to the rough surface? It will slow down and change direction or bend when it hits the rough side. (Hold the ramp at an angle and move the car so that one of the front wheels hits first and turns the car onto the rough side. Do it in slow motion a few times. If this demo works consistently for you, you may release the car and have it turn on its own.) Light, when travelling at an angle, will slow down and bend when it encounters a different material. Plastic Cardboard www.letstalkscience.ca Sandpaper Page 18 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science What happens when you look down at your feet in a swimming pool? Your feet look bigger, your legs look shorter and it looks like you legs are on an angle. This is because the light is being bent as it travels through the water. Think of this example: you are rollerblading down a smooth hill and suddenly notice a patch of grass in front of you. You try to miss it, but unfortunately, your left rollerblade runs over the grass while your right one stays on the pavement. What will happen? Your body will turn to the left, as you start to run over the grass. Since your left rollerblade suddenly slows down, but your right one keeps going at the same speed, your body is forced to make a left turn. This is the same thing that happens to a beam of light when it travels from one transparent material to another. CHOICE: This demo can be included by the facilitator if there is time. B) Broken Pencil Demo (Fill a clear cup ¾ full of water. Place a pencil in the cup at an angle. Ask the students to observe the pencil.) Does the pencil look like it is broken? Yes The light is being bent as it travels through the water, making it appear that the pencil is not straight. We have learned from our examples that when light travels from one material into another material, it may change direction and speed. This change is called refraction. Refraction only takes place if light rays enter the new material at an angle. Station Explanation At the refraction station your group will set up a flashlight so that its light shines through the paper towel tube, and then onto a comb so that you get shadows of the comb teeth on the desk. These shadows will show you what www.letstalkscience.ca Page 19 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science direction the light is travelling. Draw the shadows on your worksheet. Then you will add a glass of coloured water, look to see what happens to the shadows and draw the new shadows. Do the same thing again but this time with a lens. Hint: watch closely to see if the light changes direction as it passes through different materials. DELIVERY HINT: Make sure the flashlight is always pointing towards the window. Make the room as dark as possible, but light enough so students can still do other activities. ACTIVITY #3b: REFRACTION – MAGNIFING GLASSES (15 min.) Oral instructions Objectives of Activity To understand that we use refraction to help us see objects more clearly. Suggested Instructions, Q & A Use the magnifying glasses to read the tiny symbols on the cards. Draw the magnified images in the squares provided. ACTIVITY #3c: REFRACTION – REFRACTION VIEWERS (15 min.) Oral instructions Objectives of Activity To demonstrate that white light is made up of many colours. Suggested Instructions, Q & A Use the refraction viewers to see the colours of the rainbow. www.letstalkscience.ca Page 20 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science E. Debrief We have been learning about three things that light does. At the station where you compared the different materials that you could see through, we were looking at the transmission of light. What does the word transparent mean? It lets all the light through. What materials were transparent? Clear plexiglass, acetate, holes in the screen What does the word opaque mean? It lets no light through. What materials were opaque? Cardboard, aluminum foil, wires in the screen, paper. If light shines around an opaque object what do you get? Shadows. Was everyone able to recreate the shadows? What time of day do you cast the shortest shadows? At noon, when the sun is at its highest. What does the word translucent mean? It lets some light through. What materials were translucent? Plastic shopping bag, tissue paper, screen. Answers may be different based on many factors such as the distance the frames are held from the logos, as well as the children’s visual abilities. Transparency is a sliding scale. The screen fabric is a tricky material, as the screen fabric itself is opaque, and the spaces in between the fabric strands are transparent. Our eyes compensate for this and we see the whole material as translucent. www.letstalkscience.ca Page 21 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science What is reflection? Light bouncing. How did we use reflection to light up the picture at the end of the maze? Light was reflected from mirror to mirror. We also found out that light can be bent. What is the word for the bending of light? Refraction. What happened to the rays of light after they passed through the glass of water? The lines crossed, lines came together in a point. What happened to the rays of light after they passed through the other lens? The lines spread out. Light is refracted as it passes through a lens. Even something as simple as a glass of water can act as a lens. Eyeglasses are lenses that bend light as it travels to our eyes. They help to focus the light so we can see an object clearly. Where are some other places that lenses can be found? Our eyes, cameras, movie projectors, slide projectors, overhead projectors, microscopes, telescopes, headlights, etc. Did the magnifying glass make the image bigger or smaller? Bigger What were the 3 symbols on the cards? Smiley face Hand Candle The magnifying glasses act just like the first glass lens and bend the light reflected from the object inwards. They help us to see small things more clearly. www.letstalkscience.ca Page 22 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science The other instruments at the table were there for you to try out and to see that we use refraction in many different ways. All of these devices were designed using our knowledge of refraction of light. Were you able to see a rainbow with the refraction viewer? What colours did you see? Red, orange, yellow, green, blue, indigo, violet What is happening? As the light enters the viewer it hits the different thicknesses of plastic. These variations in thickness act like a prism, the plastic slows the light down. Imagine that this is like running through air and then running through water. White light from the sun or a flashlight is a mixture of many colours. Each colour that we see is a wavelength of light travelling at a different speed. Red light, with the longest wavelength, is bent the least by the prism and violet light, with the shortest wavelength, is bent the most. These different wavelengths are sensed by our eyes as different colours. Can you think of other things that act like prisms? Diamond rings, sun catchers, etc. All are prisms refracting light to give us a beautiful sparkle and many minirainbows. F. Take Home Activity ACTIVITY #4: MAKE A KALEIDOSCOPE (20 min.) Objective of Activity To investigate how light interacts in an optical device – a kaleidoscope. Design, make and test an optical device. www.letstalkscience.ca Page 23 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Suggested Instructions, Q & A Now we are going to make an optical device that uses some of the properties of light we have learned about today. Everyone will make a kaleidoscope to take home. Can anyone tell me what a kaleidoscope does? A kaleidoscope is an optical toy in which we can see an endless variety of beautiful colours. The word kaleidoscope has a Greek origin and means “beautiful form viewer”. Greek: kalos + eidos + scopos English: Beautiful + form + viewer The kaleidoscope was invented by Sir David Brewster in 1816 and it quickly became a popular optical toy. Can you think of names of any other optical devices that have the word “scope” in them? Microscope, telescope, oscilloscope. A microscope is a viewer for very small things. A telescope is a viewer for things that are at a distance. An oscilloscope allows us to view wave vibrations. Kaleidoscope Directions 1. Draw a design on the small piece of acetate and on the large piece of acetate using any colours with permanent marker. 2. Glue a piece of the shiny mylar onto the cardstock. 3. Fold the cardstock and mylar along the dotted lines to form a triangular prism with the mylar on the inside. 4. Tape the prism together along the seam. 5. Poke a pin through the large acetate in the middle. Then, poke the pin through the small acetate in one corner so they are held together with the pin. 6. Tape the pin and acetate pieces to one end of the tube directly above a point of the prism. 7. Look through the open end of the tube, point it towards the light and turn the large acetate with your finger. www.letstalkscience.ca Page 24 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science G. Wrap - Up What did you see in the kaleidoscope? What happens? What do the mirrors do to the design? We see lots of colours and repeated patterns of colour. The mirrors reflect the design many times. What two properties of light do our kaleidoscopes use to create the colours and patterns we see? Light passing through materials and reflection. Light comes from the source of light in the room, through the transparent, coloured acetate to our eye. Inside the kaleidoscope the light is reflected off the mirrors to produce multiple images. SAFETY: Do NOT look through your kaleidoscope directly at the sun. We have had a lot of fun today learning about light. What are the four things that we learned about light today? Light passes through different materials in different ways. Materials can be transparent, translucent and opaque. Light can be reflected. Light can be refracted or bent. What was your favourite activity today? Do you think Science is fun? Do you like Science? Do you have any questions for me? H. Glossary Artificial Light Light from electric lamps or other people-made sources of light. www.letstalkscience.ca Page 25 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Bioluminescence The production of light by living organisms. Colour The visual sensation that is produced when light of certain wavelengths reaches the retina of the eye. The colours red, orange, green, blue, indigo and violet (ROYGBIV) form the light spectrum. Concave Curving inward Convex Curving outward Fibre optics The technique of transmitting light through long, thin, flexible fibres of glass, plastic or other transparent materials; bundles of parallel fibres can be used to transmit complete messages. Focus The point at which light rays meet after they have been reflected or refracted. An image looks sharp or clear when it is in focus. Image A copy of an object that occurs when light rays are reflected off a mirror or refracted through a lens. Kaleidoscope A device that uses several mirrors, all facing inward at an angle of 60º to each other. The many reflections of coloured light inside form attractive symmetrical patterns. Lens A curved piece of glass or other transparent material that forms an image by bending light rays. www.letstalkscience.ca Page 26 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Light A special form of energy that can be seen by our eyes and makes things visible. Opaque A material that lets no light through, that is, not transparent to the human eye. Periscope A device that reflects light through two right angles and enables a person to see over or around obstacles. Prism A triangular piece of glass or other transparent material used to split white light into the colour spectrum. Ray The straight path followed by light as it travels from its source. Reflection The change in direction of a wave when it bounces off a boundary. Refraction Bending of light rays when they travel from one transparent substance to another - amount of refraction is related to the density of the substance. Shadow An area which light rays cannot reach due to an obstacle in their path. Spectrum A band of colours formed when a beam of light is broken up by being passed through some material, such as a prism. Telescope An instrument using lenses or mirrors, or both, used for making distant objects appear nearer and larger. www.letstalkscience.ca Page 27 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Total Internal Reflection A phenomenon in which light travelling from a dense to a less dense medium hits the boundary between them at an angle equal or greater to the critical angle of incidence such that instead of being refracted by entering the less dense medium, the light is completely reflected by the boundary and remains in the dense medium. Translucent A material that lets some of the light through, that is, the material allows fuzzy or unclear shapes to be seen by the human eye. Transmission How light travels through matter. How light is transmitted classifies materials as transparent, translucent or opaque. Transparent A material that lets all the light through, that is, the human eye may see through the medium easily and clearly. I. Background Information Binoculars Lenses in binoculars collect and magnify the light from objects. As light passes through the objective lenses, an upside-down reversed image of the object is produced. There are two prisms in each half of a pair of binoculars. The prisms are specially shaped and reflect light from two of their faces. One prism turns the image the right way up and the other turns it the right way around. The four successive reflections provide a long path for the light to travel within a small space. This allows binoculars to be made much shorter and more portable than telescopes. Bioluminescence Bioluminescent organisms glow because of a chemical process. Usually, a substance called luciferin reacts with oxygen in the presence of another substance, an enzyme called luciferase. The chemical energy from the reaction is turned into light and produces very little or no heat. Most bioluminescent organisms live in the sea and use this light to see where they www.letstalkscience.ca Page 28 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science are going or to search for food. Some organisms use it to draw in prey, while others use it as a defense mechanism to frighten away predators. Fireflies use light to attract a mate. Bioluminescence usually is not a steady light, either flashing on and off or glowing only when stimulated. Fireflies Fireflies light up through a process called bioluminescence. Fireflies contain specialized cells in their abdomen that make light. The cells contain a chemical called luciferin and make an enzyme called luciferase. To make light, luciferin combines with oxygen to form oxyluciferin. The luciferase speeds up the reaction. The overall reaction is: Luciferin + ATP + O2 luciferase oxyluciferin + PPi + AMP + Light The cells that make the light also have uric acid crystals in them that help to reflect the light away from the abdomen. Finally the oxygen is supplied to the cells through a tube in the abdomen called the abdominal trachea. It is not known whether the on-off switching of the light is controlled by nerve cells or oxygen supply. Eye The eye works by: light rays travelling through the eye. Light passes through the cornea and the lens. Both are convex and bend light inward. The lens in the eye is able to change shape so objects both near and far can be focused on the retina. For example, when you look at a near object, the lens bulges, causing the light rays to bend more and focus the near object on the retina. When you look at a distant object, the lens narrows, causing the light rays to bend less and focus the distant object on the retina. The image on the retina is upside down and reversed. The retina is packed with cells that sense light. Some are shaped like rods which work in dim light and form images in black and white. Some are shaped like cones and sense colour. These rods and cones send messages to the brain along the optic nerve. Farsighted A farsighted person can clearly see distant objects but is unable to focus on near objects. The eyeball is too short or the lens of the eye is too thin. www.letstalkscience.ca Page 29 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science When looking at a near object, the light entering the eye is not refracted enough. The image is focused behind the retina and as a result, is blurred. Fibre Optics Fibre optics is used to transmit most telephone calls and emails. The voice or email is converted by electronics into pulses of light and carried by optical fibre cables to their destination. There, more electronics turn the light back into sound or data. Optical fibres are made from a very thin core of glass that can refract (bend) light strongly. The core is surrounded by a coating of glass, called the cladding, which cannot bend light as much. When light enters the fibre at a certain angle, the boundary between the core and the cladding acts like a mirror and reflects it back and forth down the fibre. Light is able to travel very long distances this way. Another use for fibre optics is in endoscopes. Endoscopes are long, thin medical instruments for seeing inside the body and contain bundles of optical fibres. Images are transmitted to television screens or an eyepiece for the doctor to see. Optical Fibres Strands of glass that conduct light. The fibre is about as thin as a human hair and can carry as much information as several thousand copper telephone wires. Each fibre is made of a: Core - thin glass center of the fibre where the light travels; Cladding - an outer optical material surrounding the core that reflects the light back into the core; Buffer coating - a plastic coating that protects the fibre from damage. Thousands of these optical fibres can be arranged in bundles in optical cables. The bundles are protected by the cables outer covering called a jacket. Fluorescent Tube Fluorescence is defined as visible light given off by some substances when they absorb ultraviolet radiation. Fluorescent lights work because some materials fluoresce (absorb radiation at one frequency and then give it out at another frequency). A fluorescent bulb contains mercury gas inside a glass tube. Electricity is passed through the tube which is coated inside with fluorescent crystals, called phosphors. When this happens, the gas inside the tube becomes excited and emits ultraviolet light. Since we cannot see UV light, the phosphors absorb the UV light and convert it into visible www.letstalkscience.ca Page 30 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science light. The material also becomes hot during this process, so it also emits some light in the same way as hot objects. The advantage of fluorescent lights is they are very efficient at converting electrical energy into light, as only a few specific frequencies are used. Fluorescence can occur in nature a fluorescent rock will glow under an ultraviolet lamp. Glasses Glasses are used by people who have eyes that do not focus properly (nearsighted or farsighted). They have been used in North America for at least 700 years. The earliest glasses had convex lenses to help farsighted people focus on nearby objects. In 1784, Benjamin Franklin invented ''bifocals'' glasses with lenses split into two parts, each with a different focal length. A contact lens does the same job as an eyeglass lens, but it sits on the surface of the eye. Glow-sticks Chemical glow light sticks glow in the dark when two different chemicals are mixed together. Glow light sticks consist of one plastic casing molded into a certain shape containing a chemical fluid. Inside this casing, floating around in the fluid, are two or more brittle glass casings, containing another chemical. When the outer plastic casing is bent, the glass casings inside it break, thus releasing its chemicals. The mixture of these two different chemicals causes a chemical reaction and creates the glowing effect. Glow sticks may last up to 8 hours. It is possible to restart a used light stick by placing it in hot water for a few seconds. It is also possible to lengthen the chemical process for more than 24 hours by placing the glow stick in a freezer. Holograms 3-D photos called holograms are created with lasers. One half of the laser beam is directed onto a special holographic film, while the other half of the beam is scattered off the subject. The pattern of light recorded on the film where the two beams meet represents both how bright and how far away from the film each part of the subject is. Light shining at the developed film from certain angles reveals a 3-D image. Indiglo™ www.letstalkscience.ca Page 31 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science The basic technology behind the Indiglo™ watch is called electroluminescence, which is the conversion of electricity directly into light. In an Indiglo™ watch, a thin panel uses high voltage to energize phosphor atoms that produce light. The panel is very simple and consists of a thin glass or plastic layer coated with a clear conductor (like copper). Then, the conductor is coated with a very thin layer of phosphor. The phosphor is coated with a thin plastic and another electrode is added (like zinc sulphide). This is actually two conductors (a capacitor) with phosphor in between. When the alternating current (100-200 volts AC) is applied to the conductors, the phosphor is energized and begins to emit photons. To produce the high voltage in a watch with a 1.5 volt battery, a 1:100 transformer is used. Laser The laser was first invented in 1960. Laser is an acronym for the phrase “light amplification by stimulated emission of radiation”. Laser light is monochromatic and is made up of mainly one wavelength and appears to us as a single, very pure beam of colour. Most lasers have either gas, or a crystal such as a ruby, trapped inside a small space with mirrors at each end. They operate by a burst of very bright light or electricity which causes the gas or crystal to produce light. The colour of the light depends on the substance trapped - rubies give red lights, for example. The light then reflects back and forth off the mirrors in the cavity. Each time the light passes through the crystal or gas, it causes them to give off more light. An extremely powerful laser beam then emerges from a small hole in one of the mirrors. Some uses of lasers include medical surgery, creating holograms, reading data on compact discs and cutting metal. LCD LCD is short for Liquid Crystal Display, which is numbers shown on digital watches and calculators as black lines against a grey background. . A thin layer of a liquid crystal is sandwiched between two sheets of glass. The glass is coated with a transparent film of metal. A pattern of seven short lines that form the number 8 are etched into the top glass sheet. When a small electrical charge is applied to the short lines, it causes the liquid crystal to turn black and outline the numbers to show the time or computation. www.letstalkscience.ca Page 32 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science LED LED is short for Light-Emitting Diode. LED light is often found on stereo controls and other electronic equipment. LED light comes from two attached layers of crystal material. One material normally has too many electrons and the other has too few. When an electric current flows, the extra electrons move to the side with fewer electrons and the red light is produced. Lens A lens is a piece of transparent material that has at least one smoothly curved surface. A convex lens (bulges out) causes light to bend in and converge or come together. Objects look larger or smaller, depending on their distance from the lens. Uses of convex lenses include magnifying glasses. A concave lens (caves in) causes light to bend outward and diverge or spread out. Light rays appear to come from a virtual focal point the same side of the lens as the light enters. Concave lenses make objects look smaller. Light Light is a form of energy that we think of as travelling in waves. It forms the small visible part of the electromagnetic spectrum, which also includes radio and television waves, microwaves, infrared (heat), ultraviolet (UV), Xrays and gamma rays. The current theory is that light can travel both as waves and as tiny particles of energy called photons, but never both at the same time. Light comes from atoms, the tiny bits of matter from which everything is made. The electrons circling around every atom send out light. When an atom is given a burst of energy by, for example, an electric spark, the electron becomes energized. Light sources send out light when their atoms become energized or excited and move out further from the centre of the atom and then back again - typically when they get hot. Light is created by energy and is a form of energy itself. Each photon of light is so small that the amount of energy it contains is minute. But, a beam of light contains billions of photons and so the amount of energy it contains is quite large. Light travels in straight lines from its source. Light Bulbs The light bulb was invented by Thomas Edison in 1879. The first bulbs were made from hand blown glass bulbs, a carbonized thread (the filament), a vacuum pump to force out all of the air and a wooden screw base. The www.letstalkscience.ca Page 33 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science machine that produced the electricity was called a dynamo and the electric current was provided by way of copper wires in the bulb. Today, the electric light lamp, or incandescent light bulb, changes electrical energy into light energy. When a light switch is turned on, a current of electricity is sent through wires to the lamp. Inside the sealed glass bulb filled with an inert gas, electricity flows through a length of very thin tungsten wire suspended between two electrodes. This wire is called a filament. The filament is too thin to carry the electricity, so it overheats (2500 C) and glows white hot. Electric lamps are very inefficient, as only about 5% of the electrical energy supplied to the bulb becomes visible light. The other 95% is changed into heat. Tungsten halide bulbs operate at 3500 C, emit more light in the visible range and are brighter light sources than ordinary bulbs. Microscope The microscope was invented c. 1590 by Zacharias Janssen. Robert Hooke made compound microscopes containing two or sometimes three lenses. Most optical microscopes are compound microscopes containing at least two convex lenses. The objective lens (or lenses) near the specimen collects light reflected from it and forms a magnified image. The eyepiece lens (or lenses) magnifies the image even more. One thousand times magnification is possible. The electron microscope is used to magnify things hundreds of thousands of times. It uses beams of electrons rather than light. Light waves are too long to reflect off very, very tiny specimen. Tiny things can, however, interact with electron beams. Mirages A mirage is caused by refraction. A mirage occurs when a layer of warm air next to the ground is trapped by cooler air above. Light rays from distant objects are refracted as they pass from cool air into warmer air. Light is bent toward the horizontal line of vision and eventually it is made to travel upward by total internal reflection. The light rays appear to be coming from the ground, thus, the mirage is an upside-down 'virtual' image (an image that does not produce light). So, what appears to be water is really a reflection of the sky. Nearsighted A nearsighted person can see well close up but is unable to focus on objects a long distance away. The eyeball is too long or the lens of the eye is too www.letstalkscience.ca Page 34 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science thick. This causes the light to be refracted too much when it enters the eye. The image of a distant object is focused in front of the retina and is blurred. Night Vision Night vision equipment amplifies the moonlight and starlight reflected from objects so that they appear many times brighter. Each photon of light is converted into an electron and then each electron is multiplied into many more electrons. A screen at the end of the device glows brightly whenever one of these electrons hits it and produces a visible image. Periscope A device used for seeing over or around an obstacle; it uses the laws of reflection. What we see at the eyepiece is a reflection that has bounced from angled mirror to angled mirror inside the periscope. Primary Colours of Light The primary colours of light are red, blue and yellow. Combinations of these three primary colours can make any other colour. For example: red + yellow = orange blue + red = magenta blue + yellow = green blue + red + yellow = white Rainbows All rainbows are produced by the sun's light. After a shower, tiny round drops of water are left in the air. As sunlight enters the drops, each of the colours in the white light is refracted, or bent, by a slightly different amount. This produces all of the colours of the rainbow. The dispersed light is reflected from the back of the droplet, and returns in the observer's direction. Upon leaving the droplet, the light is again refracted and dispersed. A rainbow is the dispersing effect of millions of droplets of water. Red appears at the top of the primary bow, with orange, yellow, green, blue, indigo and violet below. The colours depend on the position of the drop in the sky. Red light is seen from raindrops at an angle of 42 degrees to the line of the horizon and blue light is seen from those at 40 degrees. All other colours of the rainbow are seen from drops between these two angles. When a secondary rainbow appears, the colours are www.letstalkscience.ca Page 35 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science reversed. Light entering the raindrops is reflected inside twice. Red light is then seen from raindrops that are at an angle of 50 degrees to the line of the horizon, and blue light from drops at an angle of 54 degrees. Neat Fact: Sir Isaac Newton was one of the first people to reason that white light was made up of many colours. He used a glass prism to split light into its separate colours. Besides the 6 main colours (red, orange, yellow, green, blue, violet), Newton distinguished a seventh colour, indigo, since he believed the number 7 has mystical significance. Reflection When light strikes a mirror it bounces off. This is called reflection. When you see the image of your face in a mirror, you are seeing the reflection of light from your face. Light reflects from a mirror at the same angle as it arrives. Reflection works this way even when it involves rough surfaces. Wherever a ray reflects from a surface it has an equal angle to the normal at that spot as it had before the reflection. When light reflects from a smooth surface, all of its rays reflect in the same direction. When light reflects from a rough surface, the rays reflect in many directions because the normals at all spots on the surface points in many different directions. Thus, you can see your reflection in a mirror, but not crumpled aluminum foil. NORMAL ANGLE of REFLECTION ANGLE of INCIDENCE Note: all things (except black things) reflect some light. For example a red scarf absorbs all colours but reflects red. That is why it appears red. Angle of Incidence: The angle at which the light is striking the mirror. Angle of Reflection: The angle at which the light is leaving the mirror. Normal: 90° from the mirrors surface www.letstalkscience.ca Page 36 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Refracting Telescopes The first telescopes were all refracting telescopes and used lenses to bend light. A simple refracting telescope has two lenses - a large objective lens with a long focal length at the end of the telescope and a smaller eyepiece lens with a short focal length into which the observer looks. The objective lens gathers the light rays from a distant object and then bends them to form an upside-down ''real'' image (an image that produces light). Light rays from this image pass through the eyepiece lens and are bent again so that they become parallel. The distant object will appear bigger. Refraction Light rays always bend away from the surface when they pass from a less dense material into a denser one. Rays bend toward the surface when they pass from denser material into a less dense material. Snell's Law of Refraction In 1621 the Dutch mathematician and astronomer Willebrord Snell (15801626) discovered the precise mathematical relationship between a beam's ''angle of incidence'' (its angle before bending) and its ''angle of refraction'' (its angle after bending). His law shows that every substance has a characteristic bending power - its ''refractive index''. The more a substance bends light, the larger its refractive index. Sources of Light There are two common ways of making light: heat something until it glows (principle used for incandescent bulbs), or excite something electrically so that it fluoresces. When an object is heated, it produces light. Hot objects emit a broad spectrum of light. The frequency and wavelength at which most of the light is emitted depends on the temperature of the object. Therefore, the hotter the object, the shorter the wavelength of energy emitted. Spotlights and Searchlights Spotlights and searchlights are also electric lights. They contain two thin carbon rods with a short gap between their ends. When an electric current is sent through the rods, the electricity jumps across the gas as a bright spark called an arc. www.letstalkscience.ca Page 37 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science The Sun The surface temperature of the sun is approximately 6000° C. The sun emits heat and a tremendous amount of light. This produced light is at a higher frequency and shorter wavelength than incandescent bulbs. Fortyone percent of the sun's light is in the visible light range. J. Suggested Resources Light Experiments http://www.hunkinsexperiments.com/themes/themes_light.htm Light Experiments http://www.scoutingresources.org.uk/badges_scientist2.html Refraction http://id.mind.net/~zona/mstm/physics/light/rayOptics/refraction/refracti on1.html Pinhole Camera http://www.exploratorium.edu/light_walk/camera_todo.html Periscope http://www.lightwave.soton.ac.uk/experiments/periscope/periscope.html Microscope http://home.houston.rr.com/molerat/micro.htm Magnifying Glass http://www.dimdima.com/work/magnify.htm Telescope http://home.houston.rr.com/molerat/tel.htm www.letstalkscience.ca Page 38 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science K. Bibliography Barkan, J. (1991). Creatures that glow. New York: Doubleday ISBN: 0-385-41978-3 Berger, M. (1987). Lights, Lenses and Lasers. New York: G. P. Putnam's Sons ISBN: 0-399-61214-9 Burnie, David (1992) Eyewitess Science Light. New York: Dorling Kindersley Inc. ISBN 1-879431-79-3 Cosner, S. (1984). The Light Bulb. New York: Walker and Company ISBN: 0-8027-6527-0 Day, T. (1998). Light. Texas: Steek – Vaughn Company Evans, D., & Williams, C. (1993) Color & Light. Richmond Hill: Scholastic ISBN 0-590-74591-3 Farndon, J. (2001). Light and Optics. New York: Marshall Cavendish Corporation ISBN: 0-7614-1090-2 Fiarotta, P & Fiarotta, N. (1999). Great Experiments with Light. Scholastic Inc. ISBN 0-439-16835-X Gore, G. (2000). Experimenting with Light and Colour. Toronto: Trifolium Books Inc. ISBN: 1-55244-036-2 www.letstalkscience.ca Page 39 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Kerrod, R., & Holgate, S.A. (2002) The Way Science Works. United States: Dorling Kindersley Inc. ISBN 0-7894-8562-1 Lauber, P. (1994). What do you see & how do you see it? – exploring light, colour, and vision. New York: Crown Publishers, Inc. Levine, S. & J. Johnstone. (1998). The Optics Book. New York: Sterling Publishing Company, Inc. ISBN: 0-8069-9947-0 Morgan, N. (1997). Lasers. Austin: Steck-Vaughn Company ISBN: 0-8172-4812-9 Stockley, C. et al. (1988). The Usborne Illustrated Dictionary of Science. England: Usborne Publishing Ltd. ISBN 0-86020-989-X Taylor, Barbara (1990) Bouncing and Bending Light. New York: Franklin Watts ISBN 0531-14014-8 Tomecek, S. (1995). Bouncing and Bending Light. New York: W.H. Freeman and Company ISBN: 0-7167-6541-1 Watson, P. (1982) Light Fantastic Great Britain. Methue Children's Books Ltd. ISBN 0-688-00969-7 Zubrowski, B.(1992) Mirrors Finding out About the Properties of Light. Boston: Bernie Zubrowski and the Children's Museum Bonus www.bonus.com/contour/beakman/http@@/www.bea.../magnify.htm www.letstalkscience.ca Page 40 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science Bonus www.bonus.com/contour/beakman/http@@/www.bea.../magnify.htm University of Arizona - Optical Sciences Center www. Optics.Arizona.EDU/K-12_Outeach/Kaleidoscopes/default.htm Ask Geeves www.ask.com Molecular Expressions - Exploring the World of Optics and Microscopy http://micro.magnet.fsu.edu/primer/java/scienceoptics/reflection/index.ht ml World book Macintosh Edition 1998 World Book, Inc and its licensors. McKay, Sidney Ellen (1998). Award Winning Science: Looking Though Kaleidoscope. Proceedings of STAO Conference. www.letstalkscience.ca Page 41 of 41 In-class workshops, Bright LIGHTS, Big Science ©2003 Let’s Talk Science