Mass-energy equation:

Einstein predicted the interconversion of matter and energy. According to him, a loss in the mass of a body provides a lot of energy. This happens in nuclear reactions. The relation between mass m and energy E is given by Einstein's mass-energy equation.

$E = mc^{2}$

Here c is the speed of light $(3\times10^{8} ms^{-1})$ The above equation shows that a tremendous amount of energy can be obtained from a small quantity of matter