The energy of a photon of wavelength (λ) is given by the expression: (Symbols have their usual meaning)
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → $hλ^{-1}c$
The energy of a photon is related to its frequency $f$ by Planck's relation:
$E = h f$
Since $f = \frac{c}{\lambda}$, where $c$ is the speed of light and $\lambda$ is the wavelength:
$E = h \frac{c}{\lambda}$
Energy of a photon: $E = \frac{h c}{\lambda}$