During forward bias in a p-n junction :

The correct answer is Option (2) → Width of the depletion layer decreases and resistance decreases

In forward bias the p-side is connected to the positive terminal. The applied voltage opposes the built-in barrier potential, so the effective barrier height falls and majority carriers cross the junction easily. The depletion layer becomes narrower and a large current flows for a small voltage, so the junction offers a low resistance.

Option (1) Width of the depletion layer increases and resistance increases — Incorrect. Both changes happen in reverse bias, where the barrier rises and the current is very small.

Option (2) Width of the depletion layer decreases and resistance decreases — Correct. The lower barrier narrows the depletion layer and lets a large current flow, so the resistance falls.

Option (3) Width of the depletion layer increases and resistance decreases — Incorrect. The depletion layer narrows in forward bias; a wider depletion layer would increase the resistance, not decrease it.

Option (4) Width of the depletion layer decreases and resistance increases — Incorrect. A narrower depletion layer lets more carriers cross, so the resistance decreases rather than increases.

NCERT (2026-27):
p-n Junction Diode Under Forward Bias – “When an external voltage V is applied across a semiconductor diode such that p-side is connected to the positive terminal of the battery and n-side to the negative terminal [Fig. 14.13(a)], it is said to be forward biased. … The direction of the applied voltage (V) is opposite to the built-in potential V₀. As a result, the depletion layer width decreases and the barrier height is reduced [Fig. 14.13(b)].”