Question

What is the speed of light in water? In glycerine?

Final Answer

- $2.25 \times 10^8 \textrm{ m/s}$
- $2.04 \times 10^8 \textrm{ m/s}$

### Solution video

# OpenStax College Physics for AP® Courses, Chapter 25, Problem 5 (Problems & Exercises)

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Video Transcript

This is College Physics Answers with Shaun Dychko. We're going to find the speed of light in different materials. We have the index of refraction as the speed of light in a vacuum divided by the speed within the material. And, we can multiply both sides by

*V*over*N*to solve for*V*. And so, we have the speed in the material is the speed of light in a vacuum divided by the index of refraction of the material. So for water, we have 3 times ten to the eight meters per second divided by the index of refraction of water, which is 1.333, giving us a speed of 2.25 times ten to the eight meters per second. And then in glycine, we have the speed of light divided by the index of refraction of glycine, which is 1.473, giving a speed of 2.04 times ten to the eight meters per second.