A light emitting diode with a band gap of 181 kJ/mol emits light in what region of the electromagnetic radiation spectrum?
A)infrared
B)ultraviolet
C)visible - blue
D)visible - red

Question

Quizplus · Accepted Answer

The energy of a photon is given by E = hc/λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength. The band gap energy is the minimum energy required to excite an electron from the valence band to the conduction band. If the band gap energy is 181 kJ/mol, then the wavelength of the emitted light is:λ = hc/E = (6.626 x 10^-34 J s)(3 x 10^8 m/s)/(181 kJ/mol)(6.022 x 10^23 mol^-1) = 680 nmThis wavelength is in the visible region of the electromagnetic spectrum, and corresponds to red light.

A Light Emitting Diode with a Band Gap of 181