Question

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

• A. 2
• B. 1/4
• C. 4
• D. 1/2

Answer 1

Answer: (A)

2

E${}_1$ = hv${}_1$ = h$\frac{c}{{\lambda }_1}$ = $\frac{hc}{2000}$
E${}_2$ = hv${}_2$ = h$\frac{c}{{\lambda }_2}$ = $\frac{hc}{4000}$
$\frac{E_1}{E_2}$ = $\frac{hc\times 4000}{2000\times hc}$ = 2