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

 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 10 8 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

 12-4 Sample Problem Sample Problem 1  12-4 Sample Problem Sample Problem 2 Material Index of Refraction (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 reflected ray refracted 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 1 st medium = Total Internal Reflection  Refraction of Light Refraction of Light