Question

Consider an electromagnetic wave that is initially in vacuum, then enters a realistic material with index of refraction n ≠ 1.

Compared to its value in vacuum, how do each of the following properties of the wave change in value?

- Frequency does not change
- Speed decrease
- Wavelength depends on n

Answer 1

The frequency is independent of refraction, so it has no effect on changing refractive index while travelling from vacuum to other mediums.

Wavelength is related directly with velocity both being proportional to each other. When light travels from vacuum to other medium, it gets into a denser medium from a rarer one, which decreases it's velocity and hence wavelength.

The amount by which light slows in a given material is described by the index of refraction, n. The index of refraction of a material is defined by the speed of light in vacuum c divided by the speed of light through the material v:

n = c/v Therefore, v= c / n

Where, n is refractive index of material,

c is speed of light in vacuum

and, v is speed of light in that medium.

And wavelength () :

When light travels from one medium to another, the speed changes, as does the wavelength. The index of refraction can also be stated in terms of wavelength:

Although the speed changes and wavelength changes, the frequency of the light will be constant. The frequency, wavelength, and speed are related by: