Question

If an electron and positron annihilate, then the energy released is

• A. $3.2\times {10}^{-13}J$
• B. $1.6\times {10}^{-13}J$
• C. $4.8\times {10}^{-13}J$
• D. $6.4\times {10}^{-13}J$

Answer 1

The correct option is B $1.6\times {10}^{-13}J$

Energy of electron $=m_e{c}^2$
Energy of positron $=m_p{c}^2$
$m_e$ = $m_p$, $c=$ speed of light.

Thus according to conservation of energy released $=2m_e{c}^2$$=2\times 9.1\times {10}^{-31}{(3\times {10}^8)}^2=1.6\times {10}^{-13}Joules.$