Looking for classes? Ksquare Career Institute, Bengaluru →
A ray of light with wavelength $\lambda$ is incident on three different photoelectric cells namely 1, 2 and 3. The threshold wavelength of these photoelectric cells are $\lambda_1$, $\lambda_2$ and $\lambda_3$, respectively and the magnitude of stopping potentials of these cells are $V_1$, $V_2$ and $V_3$, respectively. The relation between $\lambda$ and threshold wavelengths are $\lambda_1\lambda$ and $\lambda_3\gg\lambda$. The correct option is:
Detailed Solution
Photoelectric emission needs the incident wavelength to be less than the threshold wavelength. (i) $\lambda_1\lambda$: emission occurs. (iii) $\lambda_3\gg\lambda$: emission occurs. The threshold frequency of cell 3 is lower than that of cell 2 (larger threshold wavelength, smaller work function), so $V_3>V_2$. Hence $V_1=0$, $V_2<V_3$.