Question

The number of photons of light of $\overline{v}=2.5\times {10}^6{m}^{-1}$ necessary to provide $1J$ of energy are:

Answer 1

$E=\frac{nhc}{\lambda }=nhc\overline{\nu }$

where $n=$number of photons of light

$h=$ planck's constant $=6.62\times {10}^{-34}Js$

$c=$ speed of light $=3\times {10}^{8}m/s$

$\lambda =$ wavelength

$\frac{1}{\lambda }=\overline{\nu }=$ wave number $=2.5\times {10}^6{m}^{-1}$

$n=\frac{1}{6.62\times {10}^{-34}\times 3\times {10}^8\times 2.5\times {10}^6}$

$n=2.014\times {10}^{18}$