This picture actually shows both refraction (bending) and dispersion (different bending of different colors) of light.
Text Reference: Giancoli 23.4, 23.5; Haliday, Resnick, Walker 33.8
Refraction is the bending of light when it travels from one medium into another. For example, when light goes from air into water, from water into glass, from glass into air and from air into peanut butter the light is bent. The light refracts because it actually changes speed when it moves from one medium to another. Actually, this is not a special effect for light - any wave will refract when it is forced to change speed. The property of the medium that determines the speed of light in that particular medium is called the index of refraction. The index of refraction is a medium-dependent constant denoted with the letter n and is greater than or equal to 1. I should note here that all rules are made to be broken, and there are exceptions to this rule.
The speed of light in a vacuum is the fastest speed that anything can travel, and it is denoted by the letter c.
c = 3 x 10^8 m/s
It is the law. No exceptions here.
The speed of light in a medium with index of refraction n, then, is given by
v = c/n
To the extent that we study refraction, the above information won't seem very pertinent to what is coming, but like I said, it is actually the change in speed of the wave that causes it to bend.
On a cold, stormy night in February of 1621, Willebord Snell (known as Wille to his friends) discovered that the angle of refraction could be determined by a simple relationship between the angle of incidence on an interface between two media and the indices of refraction of each of the media. Lets set it up for you:
Snell's Law says that if we are measuring the angles to the normal (perpendicular) to the interface between the two surfaces, the relationship between the index or refraction and angles in each of the media is
Snell's Law. Too bad that is all he is known for.
We are going to use Snell's Law to measure the index of refraction of glass and of water in this lab. But first, do the pre-lab.
So are you excited for lab?
