Photoelectric Effect: Einstein's Equation question from MHT CET 2026 (15 May, Shift 1)

Answer: (c)

1. $\frac{hc}{\lambda} = \phi + E$ and $\frac{hc}{\lambda_1} = \phi + 2E$
2. $\frac{hc}{\lambda_1} = 2\frac{hc}{\lambda} - \phi < 2\frac{hc}{\lambda} \Rightarrow \lambda_1 > \frac{\lambda}{2}$
3. Also $\frac{hc}{\lambda_1} > \frac{hc}{\lambda} \Rightarrow \lambda_1 < \lambda$
4. So the answer is (c) $\frac{\lambda}{2} < \lambda_1 < \lambda$.