Question

What happens to an electromagnetic wave when the frequency is doubled?

A. The wavelength doubles.
B. The wavelength halves.
C. The speed doubles.
D. The speed halves.

Answer 1

The relation of wavelength and frequency is related by:

λf = c

where λ is the wavelength, f is the frequency and c is the speed of light which is constant.

Therefore, the correct answer from the choices listed above is option B. When the frequency is doubled, the wavelength halves.

Answer 2

The speed of a wave isn't influenced by frequency or wavelength.

The product of (wavelength) x (frequency) is always the same number ...
it's the wave speed. So if one of them changes, the other one changes
by the same factor in the other direction, in order to keep the product
constant.

If the frequency is doubled, then the wavelength decreases by half.