So far, we have looked at situations such as light passing from air into water or glass. In those cases, light is beant toward the normal.
What happens as light passes from water into air?
Light passing through, into the air, is bent away from the normal. As the angle of refraction -- the angle of the light passing into the air -- gets larger and larger, more and more of the light is reflected back from the surface. For some critical angle, all of the light is reflected and none of it passes into the air. For light passing from water into air, this critical angle is 49o.
This is known as total internal reflection and is important in many situations. It is used in binoculars,
It is used in "light pipes" or fiber optics that are now commonplace in communications and in medicine.
A: The index of refraction for glass is about 1.55 and the index of refraction for ethyl alcohol is 1.36. In going from a material of higher index of refraction into a material of lower index of refraction, light is bent away from the normal.
Q: If light travels from olive oil into air can the light undergo total internal reflection?
A: Total internal reflection can occur if the first index of refraction is greater than the second. Olive oil has an index of refraction of 1.47 which is greater than air's index of refraction of 1.0. Therefore, total internal reflection may occur.
(C) 2003, Doug Davis; all rights reserved