Question

What is the wavelength of the radiation with photon energy which is the mean value of photon energies of radiations with wavelengths l₁ = 4000 Å and l₂ = 6000 Å ?

• A. 5000 Å
• B. 5200 Å
• C. 5600 Å
• D. 4800 Å

Answer 1

Answer: (D)

4800 Å

Answer 2

$\frac{hc}{\lambda_{3}}$ = $\frac{\frac{hc}{\lambda_{1}} + \frac{hc}{\lambda_{2}}}{2}$

̃ $\frac{1}{\lambda_{3}}$= $\frac{1}{2}$ $\left( \frac{1}{\lambda_{1}} + \frac{1}{\lambda_{2}} \right)$

= $\frac{1}{2}$ $\left( \frac{1}{4000} + \frac{1}{6000} \right)$

̃ l₃ = 4800 Å