Question

Compare the energies of two radiations $E_1$ with wavelength $800\,nm$ and $E_2$ with wavelength $400\,nm$.

• A. $E_1 = 2E_2$
• B. $E_1 = E_2$
• C. $E_2 = 2E_1$
• D. $E_{2}=-\frac{1}{2}E_{1}$

Answer 1

Answer: (C)

$E_2 = 2E_1$

Answer 2

$E_{1}=\frac{hc}{\lambda_{1}}$, $E_2=\frac{hc}{\lambda_{2}}$ $\frac{E_{1}}{E_{2}}=\frac{hc}{\lambda_{1}} \times \frac{\lambda_{2}}{hc}$ or $\frac{E_{1}}{E_{2}}=\frac{\lambda_{2}}{\lambda_{1}}$ $=\frac{400}{800}$ $\frac{E_{1}}{E_{2}}=\frac{1}{2}$ or $E_{2}=2E_{1}$