http://www.ck12.org Chapter 20. Geometric Optics
20.3 Index of Refraction
Objectives
The student will:
- Understand how the index of refraction is defined.
- Solve problems involving the index of refraction.
- Understand Snell’s Law.
- Solve problems involving Snell’s Law.
Vocabulary
- angle of incidence
- angle of refraction
- incident ray
- index of refraction: The ratio of the speed of light through vacuumcto the speed of the light through a
particular mediumv. - refracted ray:Light rays change direction when they pass through different material.
- Snell’s Law: Expresses the relationship between the angle of incidenceθ 1 and the angle of refractionθ 2 at
the interface of two media.
Introduction
Light will change direction when it passes through different material. This is calledrefraction, as the wordrefract
means "to bend." You can see how light bends when you look through a glass of water, as shown in theFigure
20.14. It looks like the straw is broken in two pieces, but this is because the part of the straw inside the glass is not
really in the same position it appears to be.
We will show that this bending matches up to the change in how fast the wave moves. Any kind of wave can refract
if it changes speed and has room to change direction.
This site has animations of waves changing direction: http://www.s-cool.co.uk/gcse/physics/properties-of-waves/rev
ise-it/refraction-of-waves