Question

What is the ratio between the energies of two radiations one with a wavelength of $6000\mathring{A}$ and other with $2000\mathring{A}$?

Answer 1

${\lambda }_1=6000\mathring{A}$ and ${\lambda }_2=2000\mathring{A}$
$E_1=h\cdot \frac{c}{{\lambda }_1}$ and $E_2=h\cdot \frac{c}{{\lambda }_2}$
Ratio, $\frac{E_1}{E_2}=\frac{h\cdot c}{{\lambda }_1}\times \frac{{\lambda }_2}{h\cdot c}=\frac{{\lambda }_2}{{\lambda }_1}=\frac{2000}{6000}=\frac{1}{3}$
or $E_2=3E_1$.