The refractive index of a medium is defined as
- A. the speed of light in the medium divided by the speed in a vacuum
- B. the speed of light in a vacuum divided by the speed in the medium
- C. the angle of incidence divided by the angle of refraction
- D. the wavelength in the medium divided by that in a vacuum
Explanation
Since light always travels slower in a material than in a vacuum, the refractive index is always greater than one, being about 1.33 for water and 1.5 for glass. Snell's law relates the sines of the angles, not the angles themselves, which is the trap in the third option. The frequency stays the same on refraction while the wavelength shortens.
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