57. An LED is constructed from a p-n junction diode using GaAsP. The energy gap is 1.9eV. The wavelength of the light emitted will be equal to ?

57. An LED is constructed from a p-n junction diode using GaAsP. The energy gap is 1.9eV. The wavelength of the light emitted will be equal to ?

(a) \(654 \times 10^{-11}\,\text{m}\)

(b) \(10.4 \times 10^{-7 h}\,\text{m}\)

(c) \(654\,\text{nm}\)

(d) \(654\,\text{Å}\)

Answer :  (c) \(654\,\text{nm}\)

\( E_{\text{photon}} = h\nu \)

\( = \frac{hc}{\lambda} \)

\( E(\text{in eV}) = \frac{12400}{\lambda \text{ in } \text{Å}} \)

\( \lambda = \frac{12400}{1.9\,\text{eV}} \)

\( = 6200\,\text{Å} \) ( Slightly higher than this )