Question:
LED is constructed from Ga-As-P semiconducting material. The energy gap of this LED is 1.9 eV. Calculate the wavelength of light emitted and its colour.
[\(h=6.63\times10^{-34}\) Js and \(c=3\times10^{8}\) ms\(^{-1}\)]
LED is constructed from Ga-As-P semiconducting material. The energy gap of this LED is 1.9 eV. Calculate the wavelength of light emitted and its colour.
[\(h=6.63\times10^{-34}\) Js and \(c=3\times10^{8}\) ms\(^{-1}\)]
[\(h=6.63\times10^{-34}\) Js and \(c=3\times10^{8}\) ms\(^{-1}\)]
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Use \(\lambda=\frac{hc}{E_g}\) with \(E_g=1.9\times1.6\times10^{-19}\) J.
Updated On: Nov 4, 2026
- 654 nm and orange colour
- 654 nm and red colour
- 1046 nm and red colour
- 1046 nm and blue colour
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The Correct Option is B
Solution and Explanation
\(E_g=1.9\times1.6\times10^{-19}=3.04\times10^{-19}\) J.
\(\lambda=\frac{hc}{E_g}=\frac{6.63\times10^{-34}\times3\times10^{8}}{3.04\times10^{-19}}=\frac{1.989\times10^{-25}}{3.04\times10^{-19}}\approx6.54\times10^{-7}\) m \(=654\) nm.
A wavelength of about 650 nm lies in the red region of the visible spectrum (about 620-750 nm).
Answer: (2) 654 nm and red colour
\(\lambda=\frac{hc}{E_g}=\frac{6.63\times10^{-34}\times3\times10^{8}}{3.04\times10^{-19}}=\frac{1.989\times10^{-25}}{3.04\times10^{-19}}\approx6.54\times10^{-7}\) m \(=654\) nm.
A wavelength of about 650 nm lies in the red region of the visible spectrum (about 620-750 nm).
Answer: (2) 654 nm and red colour
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