When a p-n junction is forward-biased, then

The correct answer is Option (3) → Both depletion region and barrier height are reduced.

In forward bias the p-side is connected to the positive terminal and the n-side to the negative terminal. The applied voltage V opposes the built-in barrier potential \( V_0 \), so the effective barrier falls to \( V_0 - V \). The majority carriers are pushed towards the junction, and the depletion region becomes narrower. So both the barrier height and the depletion width are reduced.

NCERT (2026-27):
p-n Junction Diode Under Forward Bias – “… 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)]. The effective barrier height under forward bias is (V₀ – V).”