Which of the following electromagnetic radiations have the smallest wavelength?
A) Ultraviolet waves
B) X-rays
C) Gamma rays
D) Microwaves

Hint: We solve this question by recalling the light spectrum. The rays with higher frequency have a lower wavelength and rays with higher wavelength have a lower frequency. Frequency and wavelength are inversely proportional to each other. Refer to the diagram in a detailed solution for a better understanding.

Complete step by step solution:
In the electromagnetic spectrum there are visible and non-visible rays. The visible light region is in the middle of the spectrum. All the radioactive rays are situated on the extreme right of the spectrum and microwaves are located on the left of the spectrum.

The trend followed by the electromagnetic spectrum is that as we move from the left to right on an electromagnetic spectrum the frequency increases and the wavelength of the rays increase. So, the rays on the extreme right have the lowest wavelength.
All the radioactive rays are present on the extreme right of an electromagnetic spectrum out of which Gamma rays are the last then X-rays and then ultraviolet rays.
Hence Gamma rays have the lowest or smallest wavelength.

Option (C), Gamma rays is the correct answer.

Additional information: The increasing order of frequency of the rays in the electromagnetic spectrum is as follows Radio waves, Microwaves, Infrared, visible light, ultraviolet waves, X-rays, Gamma rays. The reverse order of this will give us the increasing order of wavelength. Hence frequency and wavelength are inversely proportional to each other.

Note: Students might get confused with the trend on the electromagnetic spectrum by taking wavelength as frequency and frequency and wavelength. It is to be remembered clearly that the wavelength decreases as we move from the left to right on an electromagnetic spectrum.