REFRACTION OF LIGHT

BEHAVIOR OF LIGHT Light acts both as a wave and as a particle Called a “wavicle” Light needs to interact with a surface in order to be seen When light encounters a boundary it can either reflect (bounce back) or refract (bend).

REFLECTION OF LIGHT Light reflects by bouncing back at the exact same angle that it encounters the surface with. Θ i = Θ r

REFRACTION OF LIGHT When light moves from one material to another, its speed changes based on the density of the new material Fastest light can travel is 3.0 x 10 8 m/s (vacuum) = c The comparison of the fastest speed to the speed in a material is called the index of refraction, n

INDEX OF REFRACTION

EXAMPLE… What is the speed of light in diamond?

SNELL’S LAW When a light ray passes from one material to another, the light ray bends depending on the ratio of the indices of refraction for the two materials. If the 1 st material has a low index of refraction, the light ray will bend toward the normal. If the 1 st material has a high index of refraction, the light ray will bend away from the normal.

EXAMPLE… A ray of light enters the water from the air at 60 ⁰ What is the angle of the light ray in the water?

TOTAL INTERNAL REFLECTION Sometimes a light ray is bent so much that it reflected back within the original material. Can only occur when traveling from a high index to a low index of refraction. Can only occur for one particular angle (called the critical angle). The refracted angle is considered to be 90 (sin 90 = 1)

EXAMPLE What is the critical angle for diamond in air?

APPARENT DEPTH