When a metal is heated to a high temperature, electrons are emitted from its surface. The process is known as
-
A.
photoelectric effect -
B.
thermionic emission -
C.
field emission -
D.
secondary emission -
E.
radioactive emission
Correct Answer: Option B
Explanation
The process by which free electrons are emitted from the surface of a metal when external heat energy is applied is called thermionic emission.