JEE MAIN - Physics (2020 - 6th September Evening Slot - No. 18)

Given the masses of various atomic particles
mp = 1.0072 u, mn = 1.0087 u, me = 0.000548 u,
$${m_{\overline v }}$$ = 0, md = 2.0141 u, where p $$ \equiv $$ proton, n $$ \equiv $$ neutron,
e $$ \equiv $$ electron, $$\overline v $$ $$ \equiv $$ antineutrino and d $$ \equiv $$ deuteron. Which of the following process is allowed by momentum and energy conservation?
n + n $$ \to $$ deuterium atom
(electron bound to the nucleus)
n + p $$ \to $$ d + $$\gamma $$
p $$ \to $$ n + e+ + $$\overline v $$
e+ + e- $$ \to $$ $$\gamma $$

Explanation

n + n $$ \to $$ deuterium atom (This is incorrect)

Correct is n + p $$ \to $$ d + $$\gamma $$

p $$ \to $$ n + e+ + $$\overline v $$
(This is incorrect as mass is increasing)

e+ + e- $$ \to $$ $$\gamma $$ (This is incorrect)

Correct is e+ + e- $$ \to $$ 2$$\gamma $$

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