The energy of a photon in a monochromatic light of wavelength $621 \mathrm{~nm}$ matches with the band gap…
The energy of a photon in a monochromatic light of wavelength $621 \mathrm{~nm}$ matches with the band gap of a semiconducting material. Then the minimum energy required to create an electron-hole pair from the semiconductor is
[Take hc $=1242 \mathrm{eV}-\mathrm{nm}$, where h is Planck's constant and $\mathrm{c}$ is speed of light in vacuum]
$3.4 \mathrm{eV}$
$1.7 \mathrm{eV}$
$2 \mathrm{eV}$
$2.2 \mathrm{eV}$
Solution
Minimum energy required $=\frac{1242}{621} \mathrm{eV}=2 \mathrm{eV}$