Solve this following
Question:

LED is constructed from Ga-As-P semiconducting material. The energy gap of this LED is $1.9 \mathrm{eV}$. Calculate the wavelength of light emitted and its colour.

$\left[h=6.63 \times 10^{-34} \mathrm{Js}\right.$ and $\left.\mathrm{c}=3 \times 10^{8} \mathrm{~ms}^{-1}\right]$

1. $1046 \mathrm{~nm}$ and red colour

2. $654 \mathrm{~nm}$ and orange colour

3. $1046 \mathrm{~nm}$ and blue colour

4. $654 \mathrm{~nm}$ and red colour

Correct Option: , 4

Solution:

$\lambda=\frac{\mathrm{hc}}{\mathrm{E}}=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{1.9 \times 1.6 \times 10^{-19}}=6.54 \times 10^{-7}$

$=654 \mathrm{~nm}$

Red color