Statement I: When ultraviolet light is incident on a photocell, its stopping potential is $V_0$ and the maximum kinetic energy of the photoelectrons is $K_{max}$. When the ultraviolet light is replaced by X-rays, both $V_0$ and $K_{max}$ increase.
Statement II: Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.
Answer: (C) Statement I is true, Statement II is false
Concept. $K_{max}=h\nu-\phi$ grows with frequency. Electrons leave with a range of speeds because those from deeper inside lose energy on the way out, even for one frequency.
Step 1. Statement I. X-rays have a higher frequency than UV, so $K_{max}$ and $V_0$ increase: true.
Step 2. Statement II. The spread of speeds is not due to a range of frequencies (it occurs with monochromatic light too): false.
Answer. Option C.
Solution by Sreeraj P, M.Sc Physics
