JEE Physics 2023 Question with Solution

Given: Two statements about the photoelectric effect are to be checked.

Find: Which option correctly identifies the truth values of Statement I and Statement II.

For Statement I, photon energy is given by

$$E = hf$$

So, higher frequency means higher photon energy. Among microwaves, infrared rays and ultraviolet rays, ultraviolet rays have the highest frequency. Therefore, ultraviolet rays are the most effective for emission of electrons from a metallic surface. Hence, Statement I is true.

For Statement II, the maximum kinetic energy of photoelectrons is given by

$$K.E_{\text{max}} = hf - hf_0$$

where $h$ is Planck's constant, $f$ is the frequency of incident light and $f_0$ is the threshold frequency.

From this equation, above threshold frequency, $K.E_{\text{max}}$ increases linearly with $f$. So it is directly proportional, not inversely proportional, to frequency. Hence, Statement II is false.

Therefore, the correct option is C.