Question

If a proton and anti-proton come close to each other and annihilate, how much energy will be released?

• A. $1.5\times 10^{- 10} \, J$
• B. $3\times 10^{- 10} \, J$
• C. $4.5\times 10^{- 10} \, J$
• D. $2\times 10^{- 10} \, J$

Answer 1

Answer: (B)

Mass of proton = mass of anti-proton
$=1.67\times 10^{- 27}kg=1 \, amu$
Energy equivalent to amu = $931MeV$ .
So, energy equivalent to $2amu$ $=2\times 931$ $MeV$
$=1862\times 10^{6}\times 1.6\times 10^{- 19}$
$=2.97\times 10^{- 10}J$
$\approx3\times 10^{- 10}J$