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Light and Optics Section 1: Intro to Electromagnetic Waves • Intro Questions: 1. What is the difference between mechanical and electromagnetic waves? 2. Name as many types of electromagnetic waves you can 3. What is the speed of light and any other electromagnetic wave in space? The Electromagnetic Wave Electric Field • Characteristics: – Require no medium – Transverse waves of oscillating electromagnetic fields – Transverse waves move perpendicular to the direction the wave moves – The electric and magnetic fields are at right angles to each other – All electromagnetic waves travel at 3.0 x 108 m/s Magnetic Field Direction of travel towards you The Electromagnetic Spectrum Wavelength Decreases Frequency Increases Energy Increases 108 Velocity = 3.0 x m/s For All Electromagnetic Waves 3.0 x 8 10V =λ•f More Penetration and Dangerous Activity 1 1. Label all the parts of the electromagnetic spectrum in order of increasing frequency. 2. Radio Waves, Microwaves, Infrared, Visible Light, Ultra Violet, X-rays, Gamma Rays 3. Label the trend lines as well Activity 1 1. 2. 3. Label all the parts of the electromagnetic spectrum in order of increasing frequency. Radio Waves, Microwaves, Infrared, Visible Light, Ultra Violet, X-rays, Gamma Rays Label the trend lines as well 4 Visible Light 1 Radio waves 2 Microwaves 3 Infrared 5 Ultra Violet 6 X-Rays 7 Gamma Rays Wavelength Decreases Frequency Increases Energy Increases More Penetration and Dangerous Section 2: Electromagnetic Wave Math V=λ•f Speed of light distancetime calculations • Velocity = 3.0 x 108 m/s for all electromagnetic waves • If you see any of these you have an electromagnetic wave and v = 3.0 x 108 m/s • Radio Waves, Microwaves, Infrared, Visible Light, Ultra Violet, X-rays, Gamma Rays Example 1 The AM radio band extends from 5.4 x 105 Hz to 1.7 x 106 Hz. What are the longest and shortest wavelengths in this frequency range? Example 1 The AM radio band extends from 5.4 x 105 Hz to 1.7 x 106 Hz. What are the longest and shortest wavelengths in this frequency range? Example 2 What is the frequency of an electromagnetic wave if it has a wavelength of 1.0 km? Example 2 What is the frequency of an electromagnetic wave if it has a wavelength of 1.0 km? Example 3 How long does it take for light from the sun to reach Earth if the sun is 1.5 x 1011 m away? Example 3 How long does it take for light from the sun to reach Earth if the sun is 1.5 x 1011 m away? Intro 1. What are the primary colors of light? 2. List the colors of the rainbow in order 3. What do all the colors of the rainbow add up to? Section 3: Visible Light and Colors Visible Light • Characteristics – “White” light is a combination of red, orange, yellow, green, cyan, blue, and violet – A prism can separate these colors out • By refraction of different wavelengths of color Visible Light 700 nm 400 nm Red orange yellow green cyan blue violet Red: • Longest Wavelength • Lowest Frequency • Least Energy Violet: • Shortest Wavelength • Highest Frequency • Most Energy Activity 2 • List the colors of the rainbow in order from lowest to highest frequency • Color this at home Lowest Frequency Highest Frequency ________ ________ ________ ________ ________ ________ ________ Activity 2 • List the colors of the rainbow in order from lowest to highest frequency • Color this at home Lowest Frequency Red orange yellow green cyan blue violet Highest Frequency • Primary Colors – Red – Blue – Green Blue Red Green • Secondary Colors: Mixture of 2 Primary Colors – Magenta (Blue and Red) Blue Magenta Red – Cyan (Blue and Green) Blue Blue Cyan Green – Yellow (Red and Green) Blue Red White Red Yellow Green Green • A mixture of all three primary colors produces white light • Primary Colors – Red – Blue – Green Blue Red Green • Since secondary colors are a mix of two primaries: • Mixing primary and secondary colors produces white light Blue White Light = Primary Color + Secondary Color Green • White Light Red= Blue + Yellow • White Light = Green + Magenta • White Light = Red + Cyan Activity 3 • Color and label the color mixture diagram White Light = Primary Color + Secondary Color White Light= ___________+ ____________ White Light= ___________+ ____________ White Light= ___________+ ____________ Activity 3 • Color and label the color mixture diagram White Light = Primary Color + Secondary Color White Light = Blue + Yellow White Light = Green + Magenta White Light = Red + Cyan White Primary colors of light Red Blue Green Primary pigments (ink) Magenta Cyan Yellow • Primary colors (light) are secondary pigments – Red – Blue – Green Red Magenta Yellow Green Blue Cyan • Primary pigments (ink) are secondary colors – Magenta – Yellow – Cyan Yellow Green Red Cyan Blue Magenta Intro • Do section 3 of your worksheets as your intro today Section 4: Refraction of Light • Optics is the science that describes the behavior and properties of light and the interaction of light with matter. • Refraction- Bending of light as it travels from one medium to another. • Refraction occurs because lights velocity changes in another medium. • Light does not need a medium but it is affected by it. Key items for refraction • Light travels from the object to the observers eyes • Light travels at different speed indifferent medium Normal Line • Terms to know: – Normal line – Angle of incidence Θi – Angle of refraction Θr Θr Slower Medium Θi • As light moves into a new medium, part of it is reflected and part is refracted (a) Into slower medium light bends toward the normal line (b) Into faster medium light bends away from the normal line • Objects appear to be in a different position due to refraction – An object “appears” to be straight ahead – Light always travels from the object to the observers eyes, bending into the new medium Cats Perspective Fishes Perspective • Index of refraction (n)- the ratio of speed of light in a vacuum to speed of light in that substance. – Always greater than 1 because light in a vacuum is the fastest (n = 1.00 for a vacuum) – Has no unit n = index of refraction c = speed of light in a vacuum v = speed of light in medium Example 4 • Tom, a watchmaker, is interested in an old timepiece that’s been brought in for a cleaning. If light travels at 1.90 x 108 m/s in the crystal, what is the crystal’s index of refraction? Example 4 • Tom, a watchmaker, is interested in an old timepiece that’s been brought in for a cleaning. If light travels at 1.90 x 108 m/s in the crystal, what is the crystal’s index of refraction? Example 5 • How fast does light travel in fluorite (n=1.434)? Example 5 • How fast does light travel in fluorite (n=1.434)? • Snell's Law- a formula that describes the angle of incidence and angle of refraction (ni)(sin Θi) = (nr)(sin Θr) ni = index of refraction of first medium (incidence side) Θi = angle of incidence nr = index of refraction of second medium (refracted side) Θr = angle of refraction (ni)(sin Θi) = (nr)(sin Θr) Can be rearranged to solve for ni Can be rearranged to solve for nr (ni)(sin Θi) = (nr)(sin Θr) Can be rearranged to solve for Θi Can be rearranged to solve for Θr Example 6 A light ray traveling through air (n=1.00) strikes a smooth, flat slab of crown glass (n=1.52) at an angle of 30.0° to the normal. a. Find the angle of refraction b. Draw a picture and label it Example 6 • A light ray traveling through air (n=1.00) strikes a smooth, flat slab of crown glass (n=1.52) at an angle of 30.0° to the normal. Find the angle of refraction. Example 7 Find the angle of refraction for a ray of light that enters a calm lake at an angle of 25° to the normal. (nair = 1.00 and nwater = 1.33) Example 7 Find the angle of refraction for a ray of light that enters a calm lake at an angle of 25° to the normal. (nair = 1.00 and nwater = 1.33) Section 5: Critical Angle • What happens when you increase the angle of incidence when going from a slow to a fast medium? • Remember: slow to fast bends away from the normal • What happens if you increase the angle of incidence beyond here? • Total internal reflection Θr nr = 1.00 (faster) ni = 1.33 (slower) Θi Click on the picture for a critical angle animation • Critical angle- Angle at which there would be no refraction; only total internal reflection. • Critical angle equation (θc = critical angle) Θr nr = 1.00 (faster) ni = 1.33 (slower) Θi Example 8 • A jeweler must decide whether the stone in Mrs. Harder’s ring is a real diamond or a less-precious zircon. He measures the critical angle of the gem and finds that it is 31.3°. Is the stone really a diamond or just a good imitation? (ndiamond = 2.41, nzircon = 1.92, nair = 1.00 ) nair always the smaller n in critical angle problems n in question: solve for this Example 8 • A jeweler must decide whether the stone in Mrs. Harder’s ring is a real diamond or a less-precious zircon. He measures the critical angle of the gem and finds that it is 31.3°. Is the stone really a diamond or just a good imitation? (ndiamond = 2.41, nzircon = 1.92, nair = 1.00 ) Intro Work on section 5 and 6 of your worksheets Intro • Study for your quiz a few minutes • Borrow a ruler if you do not have one today and tomorrow. Return them before the quiz • The quiz will take place after our lesson today Section 6: Reflection and Intro to Mirrors • Why can you see a reflection on the surface of one object but not on the surface of another? • It depends on how smooth the surface is Reflections • Planar reflection -off of a smooth surface Planar reflection • Diffuse reflection - reflection off of a rough of textured surface. Diffuse reflection Plane Mirrors • A plane mirror is a flat mirror • Plane mirrors produce images that are: – Virtual - image that appears behind the plane of the mirror. – Upright – Up in the mirror is the same as the object – Non-magnified – Appear the same size as if the object was that distance away – Reversed Concave (Converging) mirror Produce two types of images depending on where the object is located relative to the focal point • Real inverted images (object beyond focal point) • Magnified virtual upright images (object between focal point and surface of mirror) Concave (converging) mirror Why two names? – Concave: name because of shape – Converging: name because of what light does • bends inward or converges Bends inward toward the object Convex (diverging) mirror • Only produce virtual, upright, and smaller images Convex (diverging) mirror Why two names? – Convex: name because of shape – Diverging: name because of what light does • bends outward or diverges Bends outward away from the object • What kind of mirror would water act like? • Why? (What kind of image is formed here) • What kind of mirror would this be like? • Why? (What kind of image is formed here) • What kind of mirror would this be like? • Why? (What kind of image is formed here) Section 7: Planar Ray Diagram A Ray Diagram • A drawing allows you to determine the size and orientation of an image formed with a mirror or lens. • The real side of the mirror is the side the object is on Mirror The real side of a mirror The virtual side of a mirror Activity 4: Drawing a Ray Diagram in a planar mirror 1. First draw the object, the mirror plane, label p and h. (the object is traditionally drawn as an arrow) • do is the distance to the mirror from the object • ho is the height of the object do ho Object Drawing the Rays 1. Draw a ray perpendicular to the mirrors surface and include its reflection 2. Draw a single ray going at an angle away from the object to the mirror (Include its reflection) 3. Since the rays don’t cross on the real side of the mirror, after the reflection, extend them until they meet on the virtual side. 4. This is where the image would appear, draw the image, with the top being where the rays intersect 5. Then finish the labeling 1 ho Object di do 2 3 4 hi Variables you need to know • • • • do is the distance to the mirror from the object di is the distance from the mirror to the image of the mirror ho is the height of the object hi is the height of the image do di hi ho Object Image Now we can analyze the image The image formed in a planar mirror is 1. Virtual 2. Same size 3. Upright ho and hi are equal Virtual: on this side of a mirror 1 ho Object di do 2 3 4 hi Facing up Example 9 • Law of Reflection Review • Mary sees a reflection of her cat sparkles in the living room window. The image of Sparkles makes an angle of 40° with the normal, at what angle does Mary see Sparkles reflected? Θr = ? Θi = 40° Example 9 • Law of Reflection Review • Mary sees a reflection of her cat sparkles in the living room window. The image of Sparkles makes an angle of 40° with the normal, at what angle does Mary see Sparkles reflected? Θr = 40° Θi = 40° At 40° to the normal line Intro a. __________________ What is line C called above? b. __________________ What would be the angle or reflection be in the diagram above? c. __________________ What would be the angle of refraction be in the diagram above? d. __________________ What would be the critical angle above be for the light beam in a substance(n=1.59) shown above? Intro a. __________________ What is line C called above? b. __________________ What would be the angle or reflection be in the diagram above? c. __________________ What would be the angle of refraction be in the diagram above? d. __________________ What would be the critical angle above be for the light beam in the substance (n=1.59) shown above? Section 8: Concave Mirror Ray Diagram Curved Mirror Ray Diagram • More variables you need to know for a curved mirror – Center of curvature (C) – the center of the curve if it was a sphere – Focal Point (F) – ½ from the mirror to the center of curvature – Principal axis- the line that the base of the arrow is on. Principal axis C F Rules for Drawing Reference Rays (Concave Mirror) Ray Line drawn from object to mirror 1. Parallel to principal axis Line drawn from mirror to image after reflection Through focal point F 2. Parallel to principal axis Through focal point F C F The image appears where all rays intersect Activity 5 • Now analyze the image just formed • Its: – Smaller – Inverted – Real (hi is less than ho) (upside down) (on the object side of a mirror) object ho image Activity 5 hi • A convex mirror produces many different types of images • Click picture for concave mirror animation Rules for Drawing Reference Rays (Concave Mirror) Ray Line drawn from object to mirror Line drawn from mirror to image after reflection 1. Parallel to principal axis Through focal point F 2. Through focal point F Parallel to principal axis C F The image appears where all rays intersect Activity 5 • Now analyze the image just formed • Its: – Not magnified (ho = hi) – Inverted (upside down) – Real (on the object side of a mirror) object ho C F image Activity 5 Rules for Drawing Reference Rays (Concave Mirror) Ray Line drawn from object to mirror Line drawn from mirror to image after reflection 1. Parallel to principal axis Through focal point F 2. Through focal point F Parallel to principal axis C F The image appears where all rays intersect Activity 5 • Now analyze the image just formed • Its: – magnified (ho < hi) – Inverted (upside down) – Real (on the object side of a mirror) object ho C F hi image Activity 5 Rules for Drawing Reference Rays (Concave Mirror) Ray Line drawn from object to mirror Line drawn from mirror to image after reflection 1. Parallel to principal axis Through focal point F 2. Through focal point F Parallel to principal axis C F Activity 5 • Now analyze the image just formed • Its: – No image formed – Does not intersect on the real or virtual side C F Activity 5 Rules for Drawing Reference Rays (Concave Mirror) Ray Line drawn from object to mirror Line drawn from mirror to image after reflection 1. Parallel to principal axis Through focal point F 2. Through focal point F Parallel to principal axis C F Activity 5 • Now analyze the image just formed • Its: – magnified (ho < hi) – upright – Virtual (on the virtual side of a mirror) image object C ho hi F Activity 5 Section 9: Convex Mirror Ray Diagram Rules for Drawing Reference Rays (convex mirror) Ray Line drawn from object to mirror 1. Parallel to principal axis Line drawn from mirror to image after reflection 2. Through focal point F Parallel to principal axis 3. Follow the arrow tips away from the mirror back with virtual lines until they intersect Through focal point F (away from the mirror) F Activity 6 C This is where the image appeared • Now analyze the image just formed • Its: – Smaller (hi is less than ho) – Upright – Virtual (on the other side of a mirror) – A convex mirror always produces this type of image This is where the image appeared Intro • Do the following ray diagrams: • 1. • 2. F C F C 3. List the objects that are Plane Mirrors Concave Mirror Convex Mirrors Section 10: Mirror Math Lens/ Mirror Math Cheat Sheet Take out a piece of paper and copy all of this Mirror Math Equations If M is negative then the image is inverted • The object side is always positive for lenses and mirror math • The image sign depends on image location • The image here would have a positive value • The image here would have a negative value do di Positive object side Positive image side of mirror Positive focal side of mirror di • The focus is on the side of the center of curvature • The concave mirror always curves to the real side and has a positive F F Positive focal side of mirror • The focus is on the side of the center of curvature • The convex mirror always curves to the virtual side and has a negative F F Positive focal side of mirror Example 10 A concave mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. a. Find the magnification of the image. b. Draw a ray diagram of the situation C F Example 10 • A concave mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. a. Find the magnification of the image. Example 10 A concave mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. b. Draw a ray diagram of the situation C F Example 11 Mark is polishing his crystal ball. He sees his reflection as he gazes into the ball from a distance of 15 cm. a. what is the focal length of Mark’s crystal ball if he sees her reflection 4.0 cm behind the surface? b. Is the image real or virtual Example 11 Mark is polishing his crystal ball. He sees his reflection as he gazes into the ball from a distance of 15 cm. a. what is the focal length of Mark’s crystal ball if he sees her reflection 4.0 cm behind the surface? b. Is the image real or virtual Example 12 You look into an empty water bowl from 6.0 cm away and see a reflection 12 cm behind the bowl. a. What is the focal length of the bowl? b. What is the magnification of the image? Example 12 • You look into an empty water bowl from 6.0 cm away and see a reflection 12.0 cm behind the bowl. a. What is the focal length of the bowl b. What is the magnification of the image? Intro: 1. Mark looks into a concave mirror from 5 cm away. If the image appears 10 cm behind the mirror: a) What is the magnification? b) What is the focal length? Section 11: Intro to Lenses The Lens Movie Clip Types of lenses • Convex (converging) lens • Concave (diverging) lens Name for what light does is opposite of mirrors Convex (converging) Lens Why two names? – Convex: name because of shape – converging: name because of what light does • bends inward or converges Near side bends outward away from the object Concave (diverging) Lens Why two names? – Concave: name because of shape – Diverging: name because of what light does • bends outward or diverges Near side bends inward toward the object • • • • • • • • The Lens do – distance to object di – distance to image ho – height of object hi – height of image F’ – virtual focal point 2F’ – double virtual focal point F – focal point 2F – double focal point do ho di Object 2F’ 2F F’ Virtual side in lenses F Image Real side in lenses hi Section 12: Concave Lens Ray Diagram Rules for Drawing Reference Rays (concave/diverging lens) Ray Line drawn from object to lens Line drawn from mirror to image after refraction 1. Parallel to principal axis Through focal point F’ 2. Through center of lens Continue straight 3. Follow the arrow tips back to the virtual side where they intersect Activity 7 2F’ F’ The image appears where all rays intersect F 2F Concave/diverging lens • Always produces a: – Virtual – Upright – Smaller image Section 13: Convex Lens Ray Diagram Rules for Drawing Reference Rays (convex/converging lens) Ray Line drawn from object to lens Line drawn from mirror to image after refraction 1. Parallel to principal axis Through focal point F 2. Through center of lens Continue straight 3. Place the image head where the rays intersect or trace the rays to the virtual side if they don’t intersect 2F 2F’ Activity 8 F’ F • Image produced: – Outside focal point (F’): • • • • Convex/converging lens Real and inverted Outside 2F’: smaller At 2F’: same size Between 2F’ and F’: magnified – Inside focal point (F’) • Virtual and upright F F’ Section 14: Lens Math Lens Math • The object side is always positive for lenses and mirror math • The virtual and real image sides are different for lenses • The other side of the lens is positive for the image – The image here would have a positive value – The image here would have a negative value di do Positive object side Negative image side do di Positive image side of lens • To determine the sign of the focal point • Determine which way the front of the lens curves or just remember these two facts: – A convex lens always has a positive focal length • Curves to the real side of a lens – A concave lens always has a negative focal length • Curves to the virtual side of a lens Negative image and focal side of lens Positive image and focal side of lens Example 13 When Sally holds a convex lens 1.00 m from a snow-covered wall, an image of a 5.00 m distant igloo is projected onto the snow. a. What is the focal length of the lens? b. Draw a ray diagram of the situation F’ F Example 13 When Sally holds a convex lens 1.00 m from a snow-covered wall, an image of a 5.00 m distant igloo is projected onto the snow. a. What is the focal length of the lens? Example 13 When Sally holds a convex lens 1.00 m from a snow-covered wall, an image of a 5.00 m distant igloo is projected onto the snow. b. Draw a ray diagram of the situation F’ F Example 14 A concave lens is placed 5.0 cm in front of a doll. a) What is the focal length of the lens if the doll’s image appears 2.0 cm on the same side of the lens? b) Draw a ray diagram of the situation F’ F Example 14 A concave lens is placed 5.0 cm in front of a doll. a) What is the focal length of the lens if the doll’s image appears 2.0 cm on the same size of the lens? Example 14 A concave lens is placed 5.0 cm in front of a doll. a) What is the focal length of the lens if the doll’s image appears 2.0 cm on the same size of the lens? b) Draw a ray diagram of the situation F’ F Example 15 A coin collector is looking at a rare coin 1.0 cm behind a magnifying glass (convex lens) with a focal length of 5.0 cm. a. What is the distance to the image? b. What is the image’s magnification? Example 15 A coin collector is looking at a rare coin 1.0 cm behind a magnifying glass (convex lens) with a focal length of 5.0 cm. a. What is the distance to the image? Example 15 A coin collector is looking at a rare coin 1.0 cm behind a magnifying glass (convex lens) with a focal length of 5.0 cm. a. What is the distance to the image? b. What is the image’s magnification? - Intro 1. You are looking at yourself from 5cm away in a concave mirror that has a focal length of 15cm. A. What is the distance to the image? B. What is the magnification? 2. You do the same as in #1 but in a convex mirror A. What is the distance to the image? B. What is the magnification? 3. You are looking through a convex lens at an object 5cm away. The image is projected 15 cm on the same A. What is the focal length of the lens? B. What is the magnification? Intro 1. You are looking at yourself from 5cm away in a concave mirror that has a focal length of 15cm. A. What is the distance to the image? B. What is the magnification? Intro 2. You do the same as in #1 but in a convex mirror A. What is the distance to the image? B. What is the magnification? Intro 3. You are looking through a convex lens at an object 5cm away. The image is projected 15 cm on the same A. What is the focal length of the lens? B. What is the magnification? 4. A ray of light is coming from a penny at the bottom of the water and hitting the surface at an angle of 34ᵒ what is the angle of refraction. (nair =1.00 nwater =1.33) 4. A ray of light is coming from a penny at the bottom of the water and hitting the surface at an angle of 34ᵒ what is the angle of refraction. (nair =1.00 nwater =1.33) 4. A ray of light is coming from a penny at the bottom of the water and hitting the surface at an angle of 34ᵒ what is the angle of refraction. (nair =1.00 nwater =1.33) Section 15: Common Optical Instruments Common Optical Instruments • Camera- A simple camera consists of a convex lens and a light sensitive film • The diaphragm and shutter regulates how much light gets to the film. • The diaphragm controls the size of opening the light passes through • Most cameras use more than one lens today Common Optical Instruments • Telescope- Uses two lenses to enlarge an image far away. • You see an image of an image. The eyepiece lens forms an enlarged virtual image of the real image formed by the objective lens. The Eye • How the eye focuses: – The ciliary muscle around the eye changes the shape and thickness of the lens, which changes the focal length of the lens – In both cameras and the eye the image is inverted. The brain has learned to turn the image around. Defects in Vision • Farsighted (Hyperopia)- trouble focusing on objects close. The eyeball is too short or the cornea is too flat. – Focus is behind the retina without correction Defects in Vision • Nearsighted (Myopia)- trouble focusing on objects far away. The eyeball is too long or the cornea is too curved. • Focus is in front of the retina Fixing defects • Converging/convex lenses are used to correct farsightedness. • Diverging/concave lenses are used to correct nearsightedness. Section 15: Dual Nature of Light Dual Nature of Light Wave Particle Duality • Light acts as a wave (through space) and a particle (when it interacts with matter) – Waves are energy carried in the disruption of medium. Have interference patterns when they go through each other. – Particles have a mass and could not occupy the same space. Remember Interference • Within an interference pattern wave amplitudes may be increased, decreased, or neutralized Constructive Interference Causes Reinforcement Destructive Interference Causes Cancelation Interference with Waves in Water • Reinforcement and cancelation can be seen here • Huygens Principle – Huygens states light acts as a wave – Every point acts as a source of a new wave Wave Properties of Light • Single slit diffraction on visible light. • Light has Huygens property of a wave • Light fans out and actually appears wider than it should be. Young’s Interference Experiment • Young further demonstrate the wave properties of light with a double slit film. • When a monochromatic light source is used a pattern of fringes result • Young shows that light has interference based on its wave properties Particle Nature of Light • Light acts like a stream of particles when it interacts with matter • Photoelectric Effect- Ejection of electrons from certain metals when light falls upon them. – Requires a high frequency of light Dual Nature of Light Video Clip Section 16: Other Light Phenomenon Laser Light • Incoherent light- crests and troughs don’t line up • Coherent light- crests and troughs line up (same frequency, phase, and direction) • Laser- Produces coherent light with the aid of a crystal Laser Light Light sabers and Laser beams Rainbows are produced by the refraction of light Thin Films • Light from one side of a bubble cancels out light from the other side showing color from white light • Diffraction Grating can be used to disperse light into colors like a prism – A prism used refraction to disperse light – Diffraction gradients use the interference of light to produce colors Diffraction and Polarization Clip Polarization of Light • Light is an electromagnetic wave • These waves produce an electric field at a right angle to the magnetic field • Usually the rays are unpolarized which means they are oscillating in random directions. Polarized Light • Some crystals can cause unpolarized light to pass through and produce polarized light which has its electromagnetic fields aligned in the same direction. • Transmission axis- line along which light is polarized • Transmission axis- line along which light is polarized • Light at 90º to the transmission axis cannot pass through. How polarized sunglasses work • Glare – When light reflects off the ground (a horizontal surface) it is polarized horizontally. • Sunglasses stop glare – They are polarized vertically so that horizontal glare cannot get through