In an unbiased p-n junction, holes diffuse from the p-region to the n-region, because
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → hole concentration in p-region is more as compared to n-region
Charge carriers diffuse from a region of higher concentration to a region of lower concentration, just as a gas spreads out. The p-region has a large concentration of holes and the n-region very few, so the concentration gradient drives holes from p to n (and electrons from n to p).
This diffusion leaves behind immobile ions on both sides of the junction, which set up the depletion layer and the barrier potential.
Why the other options are incorrect
Option (1) free electrons in the n-region attract them. — Incorrect. Diffusion is a result of random thermal motion and the difference in concentration, not of attraction by the electrons in the n-region.
Option (2) they move across the junction by the potential difference — Incorrect. The barrier potential actually opposes the diffusion of holes; the field at the junction drives holes from n to p, which is drift, not diffusion.
Option (4) hole concentration in p-region is less as compared to n-region — Incorrect. This reverses the concentrations: holes are the majority carriers in the p-region.
Note: A similar question was also asked in CUET (UG) 2023 on 24-05-2023 (Slot 3).
NCERT (2026-27):
p-n Junction Formation – “… Similarly, in a p-type semiconductor, the concentration of holes is more than the concentration of electrons. During the formation of p-n junction, and due to the concentration gradient across p-, and n- sides, holes diffuse from p-side to n-side (p → n) and electrons diffuse from n-side to p-side (n → p).”