Question

If ${v_s},{v_x}$ and ${v_m}$ are the speed of soft gamma rays, X-rays and microwaves, respectively, in vacuum, then
A. ${v_s} > {v_x} > {v_m}$
B. ${v_s} < {v_x} < {v_m}$
C. ${v_s} > {v_x} < {v_m}$
D. ${v_s} = {v_x} = {v_m}$

Answer 1

Hint
Gamma rays, X-rays and microwaves are the types of electromagnetic radiations. These differ from each other by the frequency at which they are observed, and their corresponding wavelengths.

Complete step by step answer
Electromagnetic waves are created due to the simultaneous vibrations of the magnetic and electric fields in a direction perpendicular to each other. These waves do not need a medium to travel, and hence, are not matter dependent like the mechanical waves.
The most common example of electromagnetic radiation is light. Light consists of 7 colours that are visible to us in the electromagnetic spectrum. This visible range spans from medium to high frequency. But light is not the only electromagnetic wave that exists. Our human eye can only perceive the colours of the visible range, but above and below this range there consist many other forms of EM waves.
These waves are arranged on the spectrum in the increasing order of their frequency or the decreasing order of their wavelengths. This is because the frequency and wavelength are inversely proportional to each other. Microwaves belong to the lower frequency range, while the X-rays and the gamma-rays are on the upper side of the spectrum. But despite these differences, since these three are electromagnetic waves, they all travel in vacuum with the speed of light.
Hence, the correct answer is option (D).

Note
Gamma rays are the most abundant form of radiation in the universe. These have a very high frequency but equally low wavelength. Since these rays travel galactic distances, their wavelength increases significantly which makes it tougher to detect them using telescopes. Hence, these are detected by observing the effects they have on matter around us.