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Ch. 17 Reflection and Refraction

Ch. 17 Reflection and Refraction. Milbank High School. Sec. 17.1 How Light Behaves at a Boundary. Objectives Explain the law of reflection Distinguish between diffuse and regular reflection and provide examples Calculate the index of refraction in a medium. The Law of Reflection.

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Ch. 17 Reflection and Refraction

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  1. Ch. 17 Reflection and Refraction Milbank High School

  2. Sec. 17.1How Light Behaves at a Boundary • Objectives • Explain the law of reflection • Distinguish between diffuse and regular reflection and provide examples • Calculate the index of refraction in a medium

  3. The Law of Reflection • Smooth Surfaces • Mirrors • Angle of incidence = angle of reflection • Seemingly smooth surfaces • Walls • Paper • Actually rough surfaces • Light waves result in diffuse reflection

  4. Refraction of Light • Refraction • Change in direction or bending of light at the boundary of two media • Plastics, glass • Optically dense materials • If angle of refraction is smaller than the angle of incidence

  5. Snell’s Law • The degree of refraction depends on angle of incidence and properties of the medium • Snell’s Law • Ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant

  6. Index of Refraction and the Speed of Light • Index of refraction • Measure of how much light bends in a new medium • It bends because of a change in speed • Index of refraction nsubstance = c/vsubstance

  7. Review Questions • Could the index of refraction ever be less that 1? • What behaviors does light exhibit?

  8. Sec. 17.2Applications of Reflected and Refracted Light • Objectives • Explain total internal reflection • Define the critical angle • Explain effects caused by the refraction of light in a medium with varying refractive indices • Explain dispersion of light in terms of the index of refraction

  9. Total Internal Reflection • Occurs when light passes from a more optically dense medium to a less optically dense medium at an angle so great that there is no refracted ray • Critical angle • The incident angle that causes the refracted ray to lie right along the boundary of the substance, angle Θc sin Θc = nr/ni http://www.physics.uoguelph.ca/applets/Intro_physics/kisalev/java/totintrefl/index.html

  10. Effects of Refraction • Mirages • Index of refraction changes in hot air vs. cool air • Sunlight after the sun has set • Index of refraction changes due to the change in density of the atmosphere

  11. Dispersion of Light • Separation of light into its spectrum • Happens as light travels through a prism • Glass • Diamonds • Water • Red bent the least • Violet bent the most

  12. Rainbows • Spectrum formed when sunlight is dispersed by water droplets in the atmosphere • In afternoon, only see rainbows to the east

  13. White light separates into different colors (wavelengths) on entering the raindrop because red light is refracted by a lesser angle than blue light. On leaving the raindrop, the red rays have turned through a smaller angle than the blue rays, producing a rainbow.

  14. Sun Dog • Refraction of sunlight by ice crystals • Cirrus or cirrostratus clouds

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