Q.
The maximum wavelength of electromagnetic radiation, which can create a hole-electron pair in germanium. (Given that forbidden energy gap in germanium is 0.72eV)
Here, Eg=0.72eV =0.72×1.6×10−19J
If λ is the maximum wavelength of electromagnetic radiation which can create a hole-electron pair in germanium, then Eg=λhc
or λ=Eghc =0.72×1.6×10−196.62×10−34×3×108 =1.7×10−6m