An LED is constructed from a pn junction based on a certain semi-conducting material whose energy gap is 1.9eV. Then the wavelength of the emitted light is
2.9×10−9m
1.6×10−8m
6.5×10−7m
9.1×10−5m
A
1.6×10−8m
B
9.1×10−5m
C
2.9×10−9m
D
6.5×10−7m
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Solution
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Energy gap Eg=1.9eV
Wavelength of light emitted λ=hcEg nm where hc=1240eV
∴λ=12401.9≈650 nm =6.5×10−7m
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