Question

The band gap of indium gallium arsenide varies based on the concentration of gallium in the material. A sample of InGaAs absorbs light with a wavelength less than 1.37 microns. What is the band gap of the InGaA sample in eV?

Answer 1

Here's how I'd approach this. I might have made a mistake , so I'm thankful if someone points out any mistake.

For these problems the band gap energy is equal to the lowest photon energy absorbed.

So you can convert the wavelength (1.37 microns) to energy and express this energy in eV.\[\nu =\frac{ c }{ \lambda }\] and
\[E=h \nu\]

so \[E=\frac{ hc }{ \lambda }\]

\[E _{g}=\frac{ 6.626\times10^{-34} J s \times3\times10^{8} m/s}{ 1.37\times10^{-6} m }\]

That gives \[1.45\times10^{-19} J\] or .91 eV