A) \[1.6\times {{10}^{-8}}m\]
B) \[9.1\times {{10}^{-5}}m\]
C) \[2.9\times {{10}^{-9}}m\]
D) \[6.5\times {{10}^{-7}}m\]
Correct Answer: D
Solution :
: The wavelength of the emitted light is \[\lambda =\frac{hc}{{{E}_{g}}}\] where h is the Plancks constant, c is the velocity of light in vacuum and \[{{E}_{g}}\] is the energy gap. Here, \[{{E}_{g}}=1.9eV=1.9\times 1.6\times {{10}^{-19}}J\] \[h=6.63\times {{10}^{-34}}Js,\,\,c=3\times {{10}^{8}}m{{s}^{-1}}\] \[\therefore \] \[\lambda =\frac{(6.63\times {{10}^{-34}}Js)(3\times {{10}^{8}}m\,{{s}^{-1}})}{(1.9\times 1.6\times {{10}^{-19}})}\] \[=6.5\times {{10}^{-7}}m\]
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