25.3 The law of refraction

Learning objectives

By the end of this section, you will be able to:

• Determine the index of refraction, given the speed of light in a medium.

The information presented in this section supports the following AP® learning objectives and science practices:

• 6.E.1.1 The student is able to make claims using connections across concepts about the behavior of light as the wave travels from one medium into another, as some is transmitted, some is reflected, and some is absorbed. (S.P. 6.4, 7.2)
• 6.E.3.1 The student is able to describe models of light traveling across a boundary from one transparent material to another when the speed of propagation changes, causing a change in the path of the light ray at the boundary of the two media. (S.P. 1.1, 1.4)
• 6.E.3.2 The student is able to plan data collection strategies as well as perform data analysis and evaluation of the evidence for finding the relationship between the angle of incidence and the angle of refraction for light crossing boundaries from one transparent material to another (Snell’s law). (S.P. 4.1, 5.1, 5.2, 5.3)
• 6.E.3.3 The student is able to make claims and predictions about path changes for light traveling across a boundary from one transparent material to another at non-normal angles resulting from changes in the speed of propagation. (S.P. 6.4, 7.2)

It is easy to notice some odd things when looking into a fish tank. For example, you may see the same fish appearing to be in two different places. (See [link] .) This is because light coming from the fish to us changes direction when it leaves the tank, and in this case, it can travel two different paths to get to our eyes. The changing of a light ray’s direction (loosely called bending) when it passes through variations in matter is called refraction    . Refraction is responsible for a tremendous range of optical phenomena, from the action of lenses to voice transmission through optical fibers.