Question

The rest energy of an electron is.

• A. 510 KeV
• B. 931 KeV
• C. 510 MeV
• D. 931 MeV

Answer 1

Answer: (A)

510 KeV

Answer 2

Rest energy of an electron $r_{n} \propto n^{2}$

Here $m_{e} = 9.1 \times 10^{- 31}kg$and c = velocity of light

$\therefore$Rest energy $= 9.1 \times 10^{- 31} \times (3 \times 10^{8})^{2}joule$

$= \frac{9.1 \times 10^{- 31} \times (3 \times 10^{8})^{2}}{1.6 \times 10^{- 19}}eV = 510\mspace{6mu} keV$