JEE Physics 2025 Question with Solution

Given: The options represent possible decay processes of a neutron into a proton.

Find: The physically correct nuclear process.

Use conservation of charge, baryon number, and lepton number.

For beta-minus decay, the correct process is

$$n \rightarrow p + e^- + \overline{\nu}$$

Now compare with the listed options.

For option (3), the solution working shows

$$n \rightarrow p + e^- + \overline{\nu}$$

Charge is conserved:

$$0 \rightarrow (+1) + (-1) + 0 = 0$$

Baryon number is conserved:

$$1 \rightarrow 1 + 0 + 0 = 1$$

This is valid beta-minus decay.

For the option with neutrino instead of antineutrino,

$$n \rightarrow p + e^- + \nu$$

charge and baryon number are conserved, but lepton number is violated.

For the options containing $e^+$, charge is not conserved because

$$0 \rightarrow (+1) + (+1) + 0 = +2$$

so those processes are invalid.

Therefore, the correct physical process is

$$n \rightarrow p + e^- + \overline{\nu}$$

the solution explicitly marks option C as correct, but the listed option texts show that this process actually appears under option A. This is a source discrepancy.

Therefore, based on the solution conclusion and the provided answer key, the recorded correct option is C.

Given: A neutron decay process is to be identified from four options.

Find: Which option satisfies all conservation laws.

Particle properties used in the solution:

• Neutron: charge $0$, baryon number $1$
• Proton: charge $+1$, baryon number $1$
• Electron: charge $-1$, baryon number $0$
• Positron: charge $+1$, baryon number $0$
• Neutrino and antineutrino: charge $0$, baryon number $0$

Check the valid beta-minus decay form:

$$n \rightarrow p + e^- + \overline{\nu}$$

This satisfies

$$\text{Charge: } 0 \rightarrow +1 - 1 + 0 = 0$$ $$\text{Baryon number: } 1 \rightarrow 1 + 0 + 0 = 1$$

If a neutrino is written instead of an antineutrino, then the lepton number balance is incorrect.

If a positron is emitted in

$$n \rightarrow p + e^+ + \nu$$

or

$$n \rightarrow p + e^+ + \overline{\nu}$$

then charge becomes

$$+1 + +1 = +2$$

on the right side, so charge is not conserved.

Hence the physically correct process is

$$n \rightarrow p + e^- + \overline{\nu}$$

The extracted options place this under A, while the source solution labels the answer as C. the answer is stored as C with this discrepancy noted.