Question

An LED (Light Emitting Diode) is constructed from a p-n junction based on a certain $Ga-As-P$ semi-conducting material whose energy gap is $1.9eV$.What is the wavelength of the emitted light?

• A. $650nm$
• B. $65\mathring{A}$
• C. $800nm$
• D. $8000\mathring{A}$

Answer 1

The correct option is A $650nm$

The wavelength of emitted light
$\lambda =\frac{hc}{E_g}$
Where $E_g=$ energy gap of semiconductor
$=1.9eV$
$=1.9\times 1.6\times {10}^{-19}V$
$\lambda =\frac{6.6\times {10}^{-34}\times 3\times {10}^8}{1.9\times 1.6\times {10}^{-19}}m$
$6.5\times {10}^{-7}m$
$=650\times {10}^{-9}m$
$=650nm$