Question

When cathode rays strike a metal target of a high melting point with a very high velocity then which of the following are produced?
A. $\gamma$-rays
B. Ultrasonic
C. X-rays
D. $\alpha$-rays

Answer 1

Hint: Cathode rays are the beam of negatively charged particles. These rays on being hit with a cathode screen coated with certain molecules emit light and this effect is utilized in Cathode ray tubes.

Complete answer:
Cathode rays are electrons having high velocity. Since velocity is directly proportional to the kinetic energy thus we can say that cathode rays are the electrons of high kinetic energy. When the cathode rays strike the metal target of a high melting point such as tungsten, molybdenum, etc, with high velocity or high kinetic energy then they knock out the inner electrons of the atom of the high melting point metal target and the inner shells get ionized. To fill up this vacancy the electrons from higher energy make the transition to lower energy levels. As a result, an emission of radiation is observed. Since the atomic number of the target material is high thus the emitted radiation is X-ray.

So, the correct answer is Option C.

Additional Information:
X-rays are a part of Electromagnetic radiation, whereas alpha and beta particles constitute particle radiation. In particle radiation, the particles become fast-moving and exhibit charge and mass. Also, alpha particles are positively charged particles and beta particles are negatively charged particles.

Note: The process of large unstable atoms to attain stability by emitting the extra energy in the form of radiation is known as radioactive decay and the radiation emitted can be in the form of X-rays, gamma rays, alpha, or beta particles.