The amount of refraction in a material can be determined using the index of refraction.

The index of refraction can be used to calculate the speed of light in that material.

The greater the index of refraction, the more the speed of light will slow down in that material.

MEASURING REFRACTION

ratio of the speed of light in a vacuum to the speed of light in a medium

speed of light in air almost as fast as vacuum so it is 1.00 the higher the value, the more it will slow down

n = index of refraction

c = speed of light in a vacuum = 3.0 x 108 m/s

v = speed of light in a substance (m/s)

index of refraction also found by measuring the angles of incidence and refraction and calculating sin n = sin ∠i

sin∠R

Index of Refraction (n)

12-4 Sample Problem 1 12-4 Sample Problem 2

Material Index ofRefraction (n)

when light travels from one medium to another some of the light is reflected and some is refracted (bent)

the refraction and reflection happen at the same time.

called partial reflection and refraction. ex. looking at pond or through a window

Partial Reflection & Refraction

reflected rayrefracted ray

incident ray

when light speeds up as it enters another medium, R is greater than i∠ ∠

as i increases, refracted ray will travel along ∠boundary between 2 media

∠i now the critical angle and R is 90∠ o

if i increases even more, all light will be ∠reflected back to 1st medium = Total Internal Reflection

Refraction of Light

Total Internal Reflection