Consider the following statements with respect to the 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 among the above statements is / are correct ?

Answer: [C] Both 1 & 2

The thermionic emission is cased by electrons or ions that break loose from the metal surface due to heat energy. The minimum heat energy required to make a metal emit an electron (thermion), from its surface is called threshold energy or work function. Electron volt (eV): It is the smallest unit of work and is generally used to measure threshold energy. It is defined as the amount of work done, when a charge of 1.6 × 10–19 coulombs (charge of one electron), moves through two points in an electric field, at a potential difference of one volt.

1 eV = 1.6 × 10–19 C × V = 1.6 × l0–19 J.

The minimum temperature at which a particular material emits thermions from its surface on heating is called threshold temperature. A metal cannot emit thermions at all temperatures. The thermions are emitted by a metal only when its temperature is higher than the threshold temperature.

(b) 1eV = 1.6 × l0–19 C × 1 V = 1.6 × l0–19 J

This question is a part of GKToday's Integrated IAS General Studies Module