Q 12-11-035JEE MainJEE Main 2026 (8 Apr, Shift 2)Medium
$K_1$ and $K_2$ be the maximum kinetic energies of photoelectrons emitted from a surface of a given material for the light of wavelength $\lambda_1$ and $\lambda_2$, respectively. If $\lambda_1 = 2\lambda_2$ then the work function of material is given by :
Answer: (D) $K_2 - 2K_1$
Concept. Write Einstein's equation for both; $\lambda_1=2\lambda_2$ means the second photon has twice the energy $E$ of the first.
Step 1. Equations. $K_1=E-\phi$, $K_2=2E-\phi$.
Step 2. Eliminate $E$. $K_2-2K_1=-\phi+2\phi=\phi$.
Answer. $\phi=K_2-2K_1$ (Option D).
Solution by Sreeraj P, M.Sc Physics
