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Physics Question on Semiconductor electronics: materials, devices and simple circuits

An LEDLED is constructed from a pnpn junction based on a certain semi-conducting material whose energy gap is 1.9 eV1.9\, eV. Then the wavelength of the emitted light is

A

2.9×10−9m2.9\times10^{-9} m

B

1.6×10−8m1.6\times10^{-8} m

C

6.5×10−7m6.5\times10^{-7} m

D

9.1×10−5m9.1\times10^{-5} m

Answer

6.5×10−7m6.5\times10^{-7} m

Explanation

Solution

Given, energy gap Eg=1.9 eV=1.9×1.6×10−19 VE_{g}=1.9 \,eV =1.9 \times 1.6 \times 10^{-19}\, V We know that, Eg=hcλE_{g}=\frac{hc}{\lambda} λ=hcEg\lambda=\frac{hc}{E_{g}} Wavelength of the emitted light, λ=6.63×10−34×3×1081.9×1.6×10−19\lambda=\frac{6.63 \times 10^{-34} \times 3 \times 10^{8}}{1.9 \times 1.6 \times 10^{-19}} λ=6.5×10−7 m\lambda=6.5 \times 10^{-7}\, m