Energy gap between valence band and conduction band of a semiconductor is approximately:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 1 eV
The size of the energy gap between the valence band and the conduction band classifies a solid. A metal has no gap (the bands overlap), an insulator has a large gap (several eV, so thermal energy cannot excite electrons across), and a semiconductor has a small gap of the order of 1 eV: silicon 1.1 eV and germanium 0.7 eV. Hence zero, 4 eV and 10 eV describe a metal and insulators, not a semiconductor.
NCERT (2026-27):
Extrinsic Semiconductor – “… The difference in the resistivity of C, Si and Ge depends upon the energy gap between their conduction and valence bands. For C (diamond), Si and Ge, the energy gaps are 5.4 eV, 1.1 eV and 0.7 eV, respectively.”