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Concepts Of Physics MCQ Edition [Volume 2]PhysicsThe Nucleus

A free neutron decays into a proton, but a free proton does not decay into a neutron. This happens because

Options

  1. Aa neutron is a composite particle made of a proton and an electron, whereas a proton is a fundamental particle
  2. Bweak forces can operate in a neutron but not in a proton.
  3. Ca neutron is an uncharged particle, whereas a proton is a charged particle.
  4. Da neutron has a larger rest mass than a proton.

Correct answer

D. a neutron has a larger rest mass than a proton.

Step-by-step solution

For a spontaneous decay process to occur, the rest mass of the initial particle must be greater than the sum of the rest masses of the product particles to satisfy the principle of conservation of energy. The rest mass of a neutron is slightly greater than the rest mass of a proton ( m_n = 1.00866 u and m_p = 1.00727 u). Thus, the decay of a free neutron into a proton, an electron, and an antineutrino ( n p + e⁻ + _e ) releases energy and is energetically possible. Conversely, a free proton cannot decay into a neut

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