Question

A photon of radiation of wavelength $4000\mathring{A}$ has an energy $E$. The wavelength of photon of radiation having energy $0.5E$ will be

• A. $2000\mathring{A}$
• B. $8000\mathring{A}$
• C. $4000\mathring{A}$
• D. $6000\mathring{A}$

Answer 1

Answer: (B)

$E\propto \frac{1}{\lambda }\Rightarrow \frac{E_1}{E_2}=\frac{{\lambda }_2}{{\lambda }_1}$

$\because E_1=E,E_2=0.5E,{\lambda }_1=4000,{\lambda }_2=?$

$\therefore \frac{E}{0.5E}=\frac{{\lambda }_2}{4000}$

$\Rightarrow {\lambda }_2=\frac{4000}{0.5}=8000\mathring{A}$