Part 2: Refraction of light. In this part you will learn how light bends when it goes from glass into air. This "bending" is called refraction - it's the reason why, if you are standing in a pool of water and you reach for something at the bottom, like a coin, the coin isn't sitting where you think it; the light bends, but your brain assumes the light is traveling in a straight line. Refraction is important because without it, many optical devices (such as glasses) would not work. Materials have what is called an index of refraction which tells us how much, and in what direction, the light will bend when it enters that material. The index of refraction in a perfect vacuum (totally empty space) is 1. In air it is close to, but not exactly, equal to one - it is 1.0003, but for practical purposes we can use 1.0 for the index of refraction of air. In glass, the index of refraction is usually around 1.5, and in water, it is 1.33. Notice how the index of refraction for 2various materials is greater than 1. This is because the index of refraction is defined as the ratio of the speed of light in vacuum to the speed of light in the material. Light travels faster in vacuum than in any other material, so that means the index of refraction must always be greater than 1 for all real materials. There is a way to predict how much the light will bend when it crosses the boundary between two materials. If the light is incident from a material with index of refraction ni at an angle of 01 and, after it crosses the boundary into a material with index no it is at an angle 02, the equation relating all these quantities is called Snell's Law: m, sin & = n2 sin @2 The angle 01 is marked in the figure with one curved line and angle 02 is marked with three curved lines. In this exercise you will figure out the index of refraction of a piece of glass by observing a light ray passing through glass into air and measuring the angles 01 and 02. Watch the vide in the time interval 0:14 - 0:55 and take measurements for 3 different instances. Data: Index of refraction of glass = 1.52 Trial sin 02 % Error sin 61 2 Conclusions: 1) What conclusions can you draw between the incident and reflected angles? 2) What do you think were the main sources of errors in this part of the lab