During the formation of depletion layer around the imaginary pn-junction, electrons diffuse from n-region to p-region because.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Electron concentration in n-segment is higher than electron concentration in p-segment
Diffusion is the movement of carriers from a region of higher concentration to a region of lower concentration. At a p-n junction the n-side has many free electrons and the p-side very few, so this concentration gradient makes electrons diffuse from the n-side to the p-side (and holes from the p-side to the n-side).
Option (1) Electron concentration in n-segment is higher than electron concentration in p-segment — Correct. The higher electron concentration on the n-side drives the diffusion of electrons into the p-side.
Option (2) Holes of p-segment attract the electrons — Incorrect. Diffusion is not caused by attraction; it is a result of the difference in concentration.
Option (3) Electrons are lighter and have higher drift velocity — Incorrect. Drift velocity belongs to motion under an electric field (drift), not to diffusion; the junction field actually opposes this electron flow.
Option (4) Hole concentration in n-segment is higher than the electron concentration in p-segment — Incorrect. Holes are the minority carriers on the n-side, so their concentration there is low; in any case hole concentration does not drive the diffusion of electrons.
NCERT (2026-27):
p-n Junction Formation – “… 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).”