Question

An electron passing near a positively charged nucleus should get accelerated due to the attractive force, and it's speed should increase. But the opposite is observed! It's found to get slowed down. Why do you think?

• A. The electron's kinetic energy is converted into electrostatic potential energy
• B. The electron loses a lot of energy in radiation when its accelerated by the nucleus, resulting in a decrease in kinetic energy
• C. Law of conservation of energy doesn't apply to sub-atomic particles.

Answer 1

The correct option is B The electron loses a lot of energy in radiation when its accelerated by the nucleus, resulting in a decrease in kinetic energy

As an electron passes a highly positively charged nucleus, its trajectory gets deflected due to the electrostatic forces - giving it a centripetal acceleration. As we have studied earlier, any accelerating charged particle loses energy in radiation. The electron, in this case, will lose part of its kinetic energy in this radiation, and thus slow down!