# Find the ratio of energy of a photon of $2000A^{\large\circ}$ wavelength radiation to that of $4000A^{\large\circ}$ radiation.

$(a)\;2\qquad(b)\;1\qquad(c)\;3\qquad(d)\;4$

$E=\large\frac{hc}{\lambda}$
$E\propto \large\frac{1}{\lambda}$
$\large\frac{E_1}{E_2}=\frac{\lambda_2}{\lambda_1}$
$\Rightarrow \large\frac{4000}{2000}$
$\Rightarrow 2$
Hence (a) is the correct answer.