Four Layers | Two Layers

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The animation shows a right-traveling light wave (shown in blue) incident on a region composed of different mediums. The left-traveling wave (shown in red above it) represents the sum of all reflections of the incident wave at the boundaries between mediums (position is given in arbitrary units).

Notice that the amplitude of the waves vary with the medium in order to conserve energy. (The change in amplitude of a wave across boundaries may not be taken up in your introductory physics textbook.) You do not need to consider the amplitude change across mediums when answering this question. However, you should be able to compare the amplitudes of incident and reflected light in the same medium (see part b). Restart.

1. Rank the four mediums in terms of their indices of refraction, from smallest to greatest.
2. Compare the amplitude of incident light and reflected light in medium 1 when there are four layers and two layers. Why is the amplitude of reflected light (shown in red) in medium 1 so much smaller when there are multiple layers than when there are only two layers?

Problem authored by Melissa Dancy and Anne J. Cox.