Post on 02-Jan-2016
transcript
Chapter 29
Reflection and Refraction
• When waves interact with matter, they can be reflected, transmitted, or a combination of both.
• Waves that are transmitted can be refracted.
Reflection
• When a wave reaches a boundary between two media, usually some or all of the wave bounces back into the first medium.
• The part of the wave that comes back is the reflection.
Defining Normal?
• Normal: Perpendicular to the plane of a surface.
• The normal to the floor points straight up.
• The normal to the ceiling points straight down.
The Law of Reflection
Angle of Incidence = Angle of Reflection
Refraction • When a wave hits a boundary it changes its speed upon crossing the boundary between two media.
(Media is plural for medium)
• If that wave hits the boundary at any angle other than normal to the surface, it bends.
• This bending is called Refraction.
A Property of Matter
• Index of Refraction: A measure of how much slower light moves through a material.
• The higher the number, the slower light moves.
€
μ =Speed of light in a vacuum
Speed of light in material
Toward Normalor Away From Normal
• When light moves from a lower Index of Refraction to a higher index of refraction, the wave bends towards the normal.
• When light moves from a higher Index of Refraction to a lower index of refraction, the wave bends away from the normal.
Effects of Refraction in Daily life
• Think for a moment• Write down what is going on in each picture.
Diffraction
• Bending of waves when they encounter an obstacle.