Question

The ratio of energy of photon of $\lambda$ = 2000 A${}^o$ to that of $\lambda$ = 4000 A${}^o$

Answer 1

$E_1=h{v}_1=h$$\frac{c}{{\lambda }_1}$ $=\frac{hc}{2000}$

$E_2$ $=h{v}_2=h$$\frac{c}{{\lambda }_2}$ $=\frac{hc}{4000}$

$\frac{E_1}{E_2}$ = $\frac{hc\times 4000}{2000\times hc}=2$