For an LED to emit light in visible region of the electromagnetic spectrum, it can have energy band gap in the range of,
( Plank's constant, `h = 6.6 xx 10^(-34)` Js and speed of light, `e = 3 xx 10^(8) ms^(-1) ` in vacuum )

Options

A. `0.1` eV to `0.4` eV
B. `0.9` eV to `1.6` eV
C. `1.7` eV to `3.1` eV
D. `0.5` eV to `0.8` eV

Answer

C

Explanation

Key idea Frequency of visible rays range from
`4 xx 10^(14) Hz" to "7 xx 10^(14) Hz.`
Maximum and minimum energy of photon in visible light,
`E_(max) = hv = (6.6 xx 10^(-34)xx7 xx 10^(14))/(1.6 xx 10^(-19))`
`= 1.65 eV cong 1.7 eV`
So, the correct option matches between the energy `1.7 eV " to " 3 eV ` is (c) ,