Q. Consider the following statements regarding Thermionic Emission:

1. It is caused by electrons or ions that break loose from the metal surface due to heat energy.
2. A metal cannot emit thermions at all temperatures.

Which of the above statements is / are correct?
Answer: Both 1 and 2
Notes: Thermionic emission refers to the release of electrons from a metal surface following the absorption of sufficient heat energy. However, a metal will only emit thermions when its temperature exceeds a certain threshold, known as the threshold temperature. Therefore, both statements given in the question are correct.