The velocity of X rays is equal to that of:

Explanation

Option A: The speed of sound is the speed at which sound waves travel through a medium. Sound waves are a type of mechanical wave, which means that they require a medium to travel through. The speed of sound is different in different media, but it is always much slower than the speed of light. Option B: The speed of an electron can vary depending on its energy. Electrons with high energy can travel at speeds that are close to the speed of light, but electrons with low energy can travel much slower. Option C: Alpha particles are a type of ionising radiation that is emitted from the nuclei of radioactive atoms. Alpha particles are composed of two protons and two neutrons, and they have a positive charge. The speed of alpha particles can vary depending on their energy, but they typically travel at speeds that are much slower than the speed of light. Option D: The velocity of X-rays is equal to the speed of light and gamma rays. This is because X-rays, gamma rays, and light are all forms of electromagnetic radiation, and all electromagnetic radiation travels at the speed of light in a vacuum.