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Published byAubrey Simpson Modified over 8 years ago
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Refraction and Lenses
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Objectives Recognize situations in which refraction will occur. Identify which direction light will bend when it passes from one medium to another. Solve problems using Snell’s law.
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Refraction of Light The bending of light as it travels from one medium to another is call refraction. As a light ray travels from one medium into another medium where its speed is different, the light ray will change its direction unless it travels along the normal.
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Refraction of Light Refraction can be explained in terms of the wave model of light. The speed of light in a vacuum, c, is an important constant used by physicists. Inside of other mediums, such as air, glass, or water, the speed of light is different and is usually less than c.
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Boundary Behavior
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Refraction occurs when light’s velocity changes.
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Refraction of Light FST = Fast to Slow, Towards Normal If a ray of light passes across the boundary from a material in which it travels fast into a material in which travels slower, then the light ray will bend towards the normal line.
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Refraction of Light
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SFA = Slow to Fast, Away From Normal If a ray of light passes across the boundary from a material in which it travels slow into a material in which travels faster, then the light ray will bend away from the normal line.
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Refraction
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The Law of Refraction Index of Refraction is the ratio of the speed of light in a vacuum to its speed in a given transparent medium.
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Indices of Refraction for Various Substances
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The Law of Refraction
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Objects appear to be in different positions due to refraction. Snell’s Law determines the angle of refraction.
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Image Position for Objects in Different Media
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Conceptual Challenge H.G. Wells wrote a famous novel about a man who made himself invisible by changing his index of refraction. What would his index of refraction have to be to accomplish this?
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Conceptual Challenge Would the invisible man be able to see anything?
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Sample Problem Snell’s Law A light ray of wavelength 589 nm (produced by a sodium lamp) traveling through air strikes a smooth, flat slab of crown glass at an angle of 30.0º to the normal. Find the angle of refraction, r.
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