Question

LED is constructed from $Ga$ -As-P semiconducting material. The energy gap of this LED is $1.9 \,eV$. Calculate the wavelength of light emitted and its colour. $\left[ h =6.63 \times 10^{-34} \,Js \right.$ and $\left. c =3 \times 10^{8} ms ^{-1}\right]$

• A. $1046\, nm$ and red colour
• B. $654\, nm$ and orange colour
• C. $1046\, nm$ and blue colour
• D. $654 \,nm$ and red colour

Answer 1

Answer: (D)

$\lambda=\frac{ hc }{ E }=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{1.9 \times 1.6 \times 10^{-19}}=6.54 \times 10^{-7}$
$=654 \,nm$
Red color