Q154 / 160 · TS EAMCET 2022 (20 Jul Shift 1) · Physics
Statement (I) : By increasing the potential difference between cathode and anode continuously in a photoelectric experiment, the photo current always increases continuously.
Statement (II) : If two photons A and B of energies 2.5 $\mathrm{eV}$ and $3.5 \mathrm{eV}$ respectively fall on a metal surface of work function $2.0 \mathrm{eV}$, then the ratio of maximum kinetic energies emitted between A and B is 3 .
Statement (III) : The maximum energy needed by an electron to come out from metal surface is called the work function of the metal.
Which of the following is correct?
- AStatements I, II and III are true
- BStatements I, II are true, but statement III is false
- CStatements II, III are true, but statement I is false
- Correct answerDStatements I, II and III are false
Solution
Photocurrent will become constant after a certain potential difference between cathode and anode.
So, (I) is incorrect
Now,
$$
\frac{(\mathrm{K} . \mathrm{E})_{\mathrm{A}}}{(\mathrm{K} . \mathrm{E})_{\mathrm{B}}}=\frac{2.5-2}{3.5-2}=\frac{0.5}{1.5}=\frac{1}{3}
$$
So, (II) is incorrect
Work function is minimum energy needed to eject the electron.
So, (III) is in correct.
Hence, the correct answer is option: 'D'.