The decay of a proton to neutron is :

The decay of a proton to neutron is :
  1. not possible as proton mass is less than the neutron mass
  2. possible only inside the nucleus
  3. not possible but neutron to proton conversion is possible
  4. always possible as it is associated only with β+ decay

Solution

It is possible only inside the nucleus and not otherwise as it can not decay to a state of greater mass. Inside a nucleus however, the situation is different, as the binding energy of a nucleus provides the necessary energy to compensate for the neutron-proton mass difference.

Asked in: JEE Main 2021 (18 Mar Shift 2)

Practice more Nuclear Physics questions on Aicharya