Q 12-11-150JEE MainJEE Main 2020 (3 Sep, Shift 1)Medium
When the wavelength of radiation falling on a metal is changed from $500\ \text{nm}$ to $200\ \text{nm}$, the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to:
Answer: (D) $0.61\ \text{eV}$
Photon energies: $\dfrac{1240}{500} = 2.48$ eV and $\dfrac{1240}{200} = 6.2$ eV.
$$6.2 - \phi = 3(2.48 - \phi) \Rightarrow 2\phi = 1.24 \Rightarrow \phi \approx 0.62\ \text{eV}$$
Closest option: $0.61$ eV.
Solution by Sreeraj P, M.Sc Physics