Question

Visible light has wavelengths in the range of 400 nm to 780 nm. Calculate the range of energy of the photons of visible light.

Answer 1

${\lambda }_1=400nmto{\lambda }_2=780nm$

$h=6.63\times {10}^{-34}J-s,$

$d=3\times {10}^{5}m/s$

$E_1=\frac{hc}{{\lambda }_1}$

$=\frac{6.63\times {10}^{-34}\times 3\times {10}^8}{400\times {10}^{-9}}$

$=\frac{6.63\times 3}{4}\times {10}^{-9}$

$=4.97725\times {10}^{-19}$

$=5\times {10}^{-19}J$

$E_2=\frac{6.63\times 3}{7.8}\times {10}^{-19}$

$=2.55\times {10}^{-19}J$

So, the range is $2.55\times {10}^{-19}J\text{to}5\times {10}^{-19}$