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Chapter 29 Reflection and Refraction

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1 Chapter 29 Reflection and Refraction

2 Reflection - when a wave reaches a boundary between two media, some or all of the wave bounces back into the first medium

3 Angle of indicence – the angle made between the incident light ray and the normal
Angle of Reflection – The angle made between the reflected ray and the normal Law of Reflection: angle of incidence = angle of reflection

4 Reflection of an image on a flat mirror:
Candle appears as if it is behind the mirror

5 Virtual image – rays of light appear to originate from a point located behind the mirror. The image is called a virtual image, because light does not actually start there.

6 Diffuse Reflection – rays of light are scattered when reflected from a rough surface

7 All surfaces reflect sound (walls, ceilings, floor, furniture, people)
An echo is reflected sound All surfaces reflect sound (walls, ceilings, floor, furniture, people) When the walls of a room, auditorium, or concert hall are too reflective, the sound becomes garbled. This is due to multiple reflections called reverberations The walls of a concert hall are often designed with grooves so that the sound waves are diffused

8 Refraction: Waves bend when one part of each wave is made to travel slower (or faster) than another part Refraction is the bending of a wave due to a change in the wave speed as it passed from one medium into another

9 Refraction of sound over a lake:

10 Index of refraction – the ratio of the speed of light in a vacuum to the speed of light in a given material is called the index of refraction (n) Index of refaction (n) = speed of light in vacuum speed of light in material


12 (The Law of Refraction)
Snell’s Law (The Law of Refraction) n sinθ = n’ sinθ’

13 Mirage – A mirage is formed
due to the change in the speed of light in air of different density. Hot air = less dense Cold air = more dense

14 Dispersion – occurs when light composed of different wavelengths passes through a prism which causes separation of the light into its component colors

15 Critical Angle – A light beam that is incident upon the interface between two media is totally reflected at angles greater than the critical angle. θ Sin Θc = n Θc water: sin Θc = __1__ n sin Θc = .752 Θc = 48.8 degrees

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