Question

X-rays, gamma rays and microwaves, travelling in vacuum have
(A) Same wavelength but different velocities
(B) Same frequency but different velocities
(C) Same velocity but different wavelengths
(D) Same velocity and same frequency

Answer 1

Hint : The X-rays, gamma rays and microwaves are all waves present in the electromagnetic spectrum. All waves in the EM spectrum possess different energies which depend on their frequency.

Complete step by step answer
In general, an electromagnetic wave or ray is a type of wave which does not require a material medium to propagate through space. They can travel from one point to another without the need for air, water or any tangible medium to do so. The light we see and use in seeing (called visible light) is an example of electromagnetic waves. Other examples include X—rays, gamma rays and microwaves.
It is opposed to mechanical waves which require a medium to propagate through space i.e. move from one end to the other. Sound is an example of such waves. For example, it is believed that due to the nuclear reactions and other phenomena taking place in or around the sun, it must produce a large amount of sound. However this sound is not heard by us, because space is mostly vacuum and thus the sound waves do not have a medium to propagate the sound to us.
All electromagnetic waves have different energies and thus frequency (or wavelength). However, their speed, called the speed of light, in vacuum is independent of their frequency (or wavelength).
Hence, since X-rays, gamma rays and microwaves are all examples of EM waves, we can conclude that in vacuum, they travel at the same velocity but possess different wavelengths.
Hence, option C is correct.

Note
In application, due to their ability to travel at high speeds and through vacuum, makes them very useful in communication and radio astronomy. Our smart-phones, radio stations, television stations etcetera all communicate and transfer signals using EM waves which are at high speeds (about $ 3 \times {10^8}m/s $ ). This is why we can watch a live program happening thousands of miles away.