Question

The ratio of velocity of X-rays to that of gamma rays is ____
(a). < 1
(b). > 1
(c). 1
(d). Depends upon the ratio of their frequencies.

Answer 1

- Hint: Define the X-rays and the gamma rays. Learn about the electromagnetic spectrum or electromagnetic waves and their properties. X-ray is a high energy photon moving with the velocity of light. Gamma ray is also a high energy photon moving with the velocity of light. Take the ratio of these two to find the answer.

Complete step-by-step solution -
An X-ray, or X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometres to 10 nanometres, corresponding to frequencies in the range $3\times {10}^{15}$ Hz to $3\times {10}^{18}$ Hz and energies in the range from 124 eV to 124 keV. X-rays are part of electromagnetic spectra. Its wavelength is shorter than the visible light.
A gamma ray, or gamma radiation arises due to the radioactive decay of the radioactive elements. Gamma rays have energy generally greater than 100Kev and wavelengths shorter than the X-rays. It is also a part of the electromagnetic spectrum.
Electromagnetic waves can be defined as the waves that are created due to the vibration between the electric and magnetic field. Electromagnetic radiation refers to the electromagnetic wave. We have different electromagnetic waves depending on their frequencies or wavelengths.
 All electromagnetic moves with the same velocity i.e. with the speed of light,
Now if we consider the X-ray and the gamma ray both of them are electromagnetic radiation and both will have the same velocity $c\simeq 3\times {10}^{8}m{s}^{-1}$.
So, if we take the ratio of the velocities of X-ray and gamma ray, it will be 1.
The correct option is (C).

Note: the frequency and wavelengths of the electromagnetic radiation is related with the speed of light with the equation,
$c=\nu \lambda$
Where c is the speed of light, $\nu$ is the frequency of the electromagnetic radiation and $\lambda$ is the wavelength of the electromagnetic radiation.
So, with the change of frequency, the wavelength of the radiation will also change, because the speed of light is constant.