Download What is light?

What is light?
Light
Make a list of things that give us light.
How many can you think of?
Light
•
•
•
•
energy that you can _____.
Light is form of _______
see
Light is on kind of _____________.
radiant energy
Light comes from ______
many different _______.
sources
Some items _______
produce light while others
reflect light.
______
Light
• Is it a producer or a reflector?
– Candle
– Mirror
– Sun
– Flashlight
– Jupiter
producer
producer
producer
producer
producer
reflector
reflector
reflector
reflector
reflector
Light
• Name four other objects that produce light.
fire
stars
lantern
Light bulb
lamp
laser
candles
lightning
The sun
Fireflies
Flashlights
Light
• Name four other objects that reflect light.
The moon
Metal
Glass
Water
Mirrors
Snow
Flashlights
Think About It
• Where do you sit when you watch television?
You sit in front of the television to watch it.
Laser Pointer
• Turn off the classroom lights.
• Carefully point a laser pointer at a wall.
• Clap chalk erasers together ( or shake a nylon
bag of flour) between the wall and the laser
pointer.
• Record your observations:________________
_____________________________________
_____________________________________
How Does Light Travel?
straight line
• Light ______
travels in a __________.
• Can you think of some real-life examples of
light traveling in a straight line?
Television
Flashlight
Laser
Lamp
Light Experiments
• Each light source will be observed for five
characteristics
1. Color of the light
2. Intensity (Brightness)
3. Heat produced
4. How the light travels
5. Real life uses
Light Experiments
1. Color of the light
– Turn on the light.
– What color is it?
– Record this information
Light Experiments
2. Intensity (Brightness)
– Turn on the light.
– How bright is it?
– Can look at it directly without hurting your eyes?
(Use caution!)
– Rank the intensity on a scale of 1-5 with 1 being
very weak and 5 being too bright to look at.
– Record this information
Light Experiments
3. Heat produced
– Turn on the light
– Place your hand in front of the beam.
– How much heat do you feel? How long can you
leave your hand there? (Use caution!)
– Rank the heat on a scale of 1-5 with 1 being very
weak or cool and 5 being very hot.
– Record this information
Light Experiments
4. How the light Travels
– Turn on the light.
– We know light travels in a straight line.
– How do the individual light beams travel from this
light source? Are they all forced in one direction,
or are they able to travel in many directions?
– Illustrate low the light travels from its source
Light Experiments
5. Real life uses
– What would you use this light for in real life?
– Think about its properties. What uses does it
have? When have you used a similar light? Why?
– Examples:
Light an entire room
Look down a tiny hole
Find shoes in a dark closet
Highlight a word on a screen
Point to a star during a show
Light the Earth
Find a missing ball at night
Tell stories in the dark
Holiday decorations
Carry with you in a backpack
Signal to a friend across the
street
– Record at least one use per light source
Light Experiments
Light
Source
Color
of the
Light
Intensity
or
Brightness
Heat
Produced
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Illustrate
how it
Travels
Real Life
Uses
Light Experiments
Light
Source
Color
of the
Light
Intensity
or
Brightness
Heat
Produced
12345
12345
12345
12345
12345
12345
Illustrate
how it
Travels
Real Life
Uses
Reflection
absorbed by a
reflected or ________
• Light can be ________
surface.
Bounces off that
reflected it __________
• When light is ________,
surface.
mirror
– Example: ________
trapped by that
• When light is _________,
absorbed it is _______
surface.
Your body
– Example: __________
reflected off a surface in a special
• Light is _________
way.
Partner Activity: Bouncing Tennis Balls
• Illustrate what you observed while rolling,
bouncing, and catching the tennis ball.
Demonstration: Basketball
• Illustrate what you observed while bouncing
and catching the basketball.
Light Reflection
basketball actually
tennis ball and the _________
• The __________
represent what happens to ____
light as it is
________.
reflected
light hits a _________
reflective surface, like a
• When ____
______,
mirror it will ___________
bounce back at the
Same angle
__________.
strikes a surface is
• The angle at which light ______________
angle of incidence
the _______________.
Light Reflection
reflects off a surface
• The angle at which light __________
is the ________________.
angle of reflection
• The angle of incidence is 

=
to
the angle of reflection.
light strikes a ______
mirror at a
• Example: When _____
45 angle, it is reflected at a ____
45 angle.
____
• Draw and label an illustration of this property
of light.
Reflection Activities
• Review about light and reflection
– Light travels in a straight line
– Angle of Incidence
– Angle of Reflection
– Angle of Incidence = Angle of Reflection
Reflection Activities
Group Reflection Challenge
• Can you move light? Can you use what you
know about the angle of incidence and the
angle of reflection to move light? Let’s find
out!
Reflection Activities
• Set up: Stand the textbook up on the desk.
Lay the flashlight on a desk facing one cover of
the textbook. Turn on the flashlight, so you
can see the light on the cover.
Reflection Activities
• The Challenge: Move the light from one side
of the text book to the other, but the rules
are: you cannot move the flashlight or the
textbook. You may only use the mirrors and
what you know about light.
• When you have successfully found the
solution, illustrate and label your solution.
Reflection Activities
• Class Reflection Challenge:
– Have we really mastered how light moves? Let’s
find out!
– Give each student a mirror. The teacher will
carefully point a laser pointer into one mirror.
Let’s see if we can get the light to reflect in every
other mirror in the classroom.
Reflection Activities
• What worked well?
• What didn’t?
• Why?
Reflection Activities
• What would you do differently?
• What is our record for the most number of
mirrors reflected?
Mirrors that Multiply
• Test angle AOJ. How many faces do you see?
• Test angle BOI. How many faces do you see?
• Test angle COH. How many faces do you see?
• Test angle DOG. How many faces do you see?
• Test angle EOF. How many faces do you see?
Mirrors that Multiply
•
•
•
•
What pattern do you see?
fewer faces.
The larger the angle, the _____
more faces.
The smaller the angle, the _____
Why?
As the angle gets smaller, the light is able
to reflect back and forth in the mirror more
frequently resulting in more images.
Butterfly Design
• We can use mirrors to create designs. We can
also place mirrors on existing patterns to
create new designs.
• Using a single mirror to reflect portions of the
butterfly picture, you will create a new design.
Reflection Experiments
• We know light reflects off a mirror.
• We’ve done many challenges and activities
using mirrors to reflect light.
• Is a mirror the only thing that can reflect light?
No
• Today we’ll experiment with different surfaces
to see if they will reflect light.
Reflection Experiments
•
•
•
•
•
Sandpaper
Wax Paper
Small White Board
Smooth Foil
Crumpled Foil
•
•
•
•
•
•
White Paper
Canning Jar Lid
Colored Cellophane
Black Paper
Jelly Jar
Saran Wrap
Reflection Experiments
• Turn off the classroom lights.
• Test each item by placing it on a desk and
shining a flashlight on the surface.
• Reflect the light onto a plain piece of white
paper.
• Record your observations about the reflection
including size and intensity.
Reflected, Absorbed, or Transmitted?
• Light that _____________
passes through matter is
transmitted by the material.
__________
transmitted some of it is
• If light is not __________,
reflected
________.
transmitted or ________,
reflected it is
• If light is not __________
________.
absorbed
Reflected, Absorbed, or Transmitted?
• There are three types of materials:
1. Transparent: light is transmitted (passes
through)
2. Translucent: some light is transmitted, some is
reflected and scattered
3. Opaque: light is absorbed (not transmitted
or reflected)
Transparent, Translucent, or Opaque?
Transparent
Translucent
Opaque
Refraction
Activity: Cup of Water
• Put your thumb in the glass of water. What do
you observe?
• Put a drinking straw or pen/pencil in the glass
of water. What do you observe?
Thumb in the Cup of Water
Illustrate
Straw in the Cup of Water
Illustrate
Refraction
water it appears
• When an object is placed in a glass of _____
broken or shifted to the side This is because of
to be ________________________.
light refraction
________.
• Light changes ________
direction when it enters a new
________.
medium
substance through which a _____
wave is
• A medium is any _________
__________.
transmitted
• Example: Light
____ is traveling from the overhead light
air When the _______
light
bulbs through ___.
enters the cup
medium This causes the
water it enters a new ________.
of _____,
light to change _________.
direction
_____
Refraction
air travels ____.
fast
• Light in ___
• Light in _____
water travels ___________.
more slowly
slows down it changes
• When light ___________,
direction
________.
direction or _____,
bends it is
• When light changes ________
refraction
called _________.
Refraction caused by the change of the
• _________is
speed of light as it travels through different
____________
mediums
________.
Activity: Throwing Contest
• Who has a great throwing arm?
• Who won?
laser
• Why?
Speed of Light
• The speed of light is _____________________
186,000 miles per second
times around the
• That is the same as 7.5
_____________________
Earth in 1 second
______________.
air When it
• This is how fast light travels in ___.
enters a new ________
medium (like water), it slows
down. The result is _________.
refraction
Speed of Light
• Look at the cup from the side so you can still
see the bottom of the inside of the cup, but
you cannot see the coin glued to the bottom.
• Slowly pour water into the cup until you see
the coin appear.
• Why does it work?
Refraction
Refraction Experiments
• Variable: Amount of Water
• First, let’s experiment by changing the amount of
water and see how it affects refraction.
• We will measure 50 mL, 100 mL, 150 mL, and 200
mL of water into four different clear plastic cups.
• Place a drinking straw in each cup being sure the
angle of the straw is the same for each container.
• Record your observations.
Refraction Experiments
50 mL of Water
100 mL of Water
150 mL of Water
200 mL of Water
Illustrate
Illustrate
Illustrate
Illustrate
Observation
Observation
Observation
Observation
Refraction Experiments
• Variable: Type of Liquid
• Now let’s experiment by changing the type of
liquid and see how it affects refraction.
• We will measure 100 mL of water, vegetable oil,
karo syrup, and rubbing alcohol into four
different clear plastic cups.
• Place a drinking straw in each cup being sure the
angle of the straw is the same for each container.
• Record your observations
Refraction Experiments
100 mL of Water
100 mL of
Vegetable Oil
100 mL of Karo
Syrup
100 mL of Rubbing
Alcohol
Illustrate
Illustrate
Illustrate
Illustrate
Observation
Observation
Observation
Observation
Color of Light
• Light _______
travels in ______.
waves
Color of Light
• __________
Frequency is the measure of the number of
waves that pass by a given point in one second.
______
light is one kind of _______energy.
radiant
• Remember, ______
waves of all different
• Radiant energy includes ______
wavelengths and ___________.
frequencies
___________
Radiant energy are
• When all the types of _____________
order we have the
arranged in ______,
Electromagnetic Spectrum
_______________________.
Color of Light
Color of Light
Radio: Yes, this is the same kind of energy that radio
stations emit into the air for your stereo to capture
and turn into your favorite tunes. But radio waves
are also emitted by other things…such as stars and
gases in space. You may not be able to dance to
what these objects emit, but you can use it to learn
what they are made of.
Color of Light
Microwaves: They will cook your popcorn in just
a few minutes! Microwaves in space are used by
astronomers to learn about the structure of
nearby galaxies, and our own Milky Way!
Color of Light
Infrared: We often think of this as being the
same thing as ‘heat’, because it makes our skin
feel warm. In space, IR light maps the dust
between stars.
Color of Light
Visible: Yes, this is the part that our eyes see.
Visible radiation is emitted by everything from
fireflies to light bulbs to stars…also by fastmoving particles hitting other particles.
Color of Light
Ultraviolet: We know that the Sun is a source of
ultraviolet (or UV) radiation, because it is the UV
rays that cause our skin to burn! Stars and other
“hot” objects in space emit UV radiation.
Color of Light
X-rays: Your doctor uses them to look at your
bones and your dentist to look at your teeth.
Hot gases in the Universe also emit X-rays.
Color of Light
Gamma-rays: Radioactive materials (some natural and
others made by man in things like nuclear power
plants) can emit gamma-rays. Big particle accelerators
that scientists use to help them understand what
matter is made of can sometimes generate gammarays. But the biggest gamma-ray generator of all is the
Universe! It makes
gamma radiation in all
kinds of ways.
Color of Light
http://imagine.gsfc.nasa.gov/docs/science/kno
w_l1/emspectrum.html
Visible light
• We can only see one portion of the
electromagnetic spectrum. That portion is called
visible light
__________.
• What color is the light from most light bulbs? white
white light, it is actually made
• Although we see _____
up of many ______.
colors
red, orange,
• The colors of the spectrum are: ____________
yellow, green, blue, violet
______________________
An easy way to remember these colors in order is
ROY G. BiV
__________
Class Activity: Prism Glasses
White light appears while to our eyes, but it is
actually made up of the colors of the visible light
spectrum. Let’s use glasses with special lenses
to help us see these colors. Record your
observations.
Class Activity: Prisms
Prisms separate light into the colors of the
spectrum. Use a prism and a flashlight to see if
you can create a rainbow. What technique
works best?
• Is a prism the only way we see a rainbow? No
• When do you usually see a natural rainbow?
After rain
• How was the rainbow created? What caused
the sunlight to separate?
The water vapor left in the air after a rain storm
acts as a prism to separate the light.
Activity: Blending Light
• We can use a prism to separate the colors of
white light, so we can see all the colors of the
spectrum. Is it possible to blend the colors of
light and make white? Let’s find out.
• The primary colors of pigment (paint) are red,
yellow, and blue.
• We can mix these colors to make secondary or
tertiary colors.
• If you mix all the primary colors, you get “yuck.”
Activity: Blending Light
• The primary colors of light are red, green, and
blue.
• What happens if we mix them together?
• Record your observations.
Colors
• If light is made of all the colors of the
spectrum, how do we see certain colors?
• Why do we see white, black, or red?
• Illustrate and explain.
Colors
Why we see white:
• All the colors of the spectrum strike the surface.
• All the colors of the spectrum are reflected to our
eyes.
Colors
Why we see black:
• All the colors of the spectrum strike the surface.
• All the colors of the spectrum are absorbed.
(None are reflected)
Colors
Why we see red:
• All the colors of the spectrum strike the surface.
• Red is reflected to our eyes.
• The rest of the colors are absorbed.
Colors
Now try two on your own…
• Why we see yellow:
• All the colors of the spectrum strike the surface.
• Yellow is reflected to our eyes.
• The rest of the colors are absorbed.
• Why we see green:
• All the colors of the spectrum strike the surface.
• Green is reflected to our eyes.
• The rest of the colors are absorbed.
Summary
•
•
•
•
reflected (__________)
bounced off
Light can be ________
absorbed (______)
trapped
Light can be ________
refracted (____)
bent
Light can be ________
separated (_____________)
creates rainbow
Light can be _________
Color of Light Experiment
Test each object according to the chart. Record
the color observed.
Object
Color:
Red
Orange
Yellow
Red
Filter
Orange
Filter
Yellow
Filter
Green
Filter
Blue
Filter
Violet
Filter
Color of Light Experiment
Object
Color:
Green
Blue
Violet
White
Red
Filter
Orange
Filter
Yellow
Filter
Green
Filter
Blue
Filter
Violet
Filter
Color of Light Experiment
Layer the colored filters and see what effect are
created. Record your results.