Question

The semiconductor used for fabrication of visible LEDs must atleast have a band gap of 

(1) 1.1 eV 

(2) 1.8 eV 

(3) 2.1 eV 

(4) 3.0 eV

Answer 1

Correct option : (2) 1.8 eV

Explanation: 

Spectral range of visible light is from 0.4 µm to 0.7 µm. i.e. from about 3 eV to 1.8 eV. Hence semiconductor used for fabrication of visible LEDs must have at least a gap of 1.8 eV.