Q. No.Consider a beam of electrons (each electron with energy \(E_0)\) incident on a metal surface kept in an evacuated chamber. Then:
1.
no electrons will be emitted as only photons can emit electrons.
2.
electrons can be emitted but all with energy, \(E_0\).
3.
electrons can be emitted with any energy, with a maximum of \(\mathrm{E}_0-\phi\) (\(\phi\) is the work function).
4.
electrons can be emitted with any energy, with a maximum \(E_0\).
The threshold frequency for a photosensitive metal is \(3.3\times10^{14}~\text{Hz}\). If the light of frequency \(8.2\times10^{14}~\text{Hz}\) is incident on this metal, the cutoff voltage for the photoelectric emission will be:
| 1. | \(1~\text{V}\) | 2. | \(2~\text{V}\) |
| 3. | \(3~\text{V}\) | 4. | \(5~\text{V}\) |
A light of wavelength \(\lambda \) is incident on the metal surface and the ejected fastest electron has speed \(v.\) If the wavelength is changed to \(\frac{3\lambda}{4},\) then the speed of the fastest emitted electron will be:
| 1. | smaller than \(\sqrt{\frac{4}{3}}v\) |
| 2. | greater than \(\sqrt{\frac{4}{3}}\)\(v\) |
| 3. | \(2v\) |
| 4. | zero |
The work functions for metals \(A,B,\) and \(C\) are respectively \(1.92\) eV, \(2.0\) eV, and \(5\) eV. According to Einstein's equation, the metals that will emit photoelectrons for a radiation of wavelength \(4100~\mathring{A}\) is/are:
1. None
2. \(A\) only
3. \(A\) and \(B\) only
4. All the three metals
1. \(2\times 10^7~\text{m/s}\)
2. \(2\times 10^6~\text{m/s}\)
3. \(8\times 10^5~\text{m/s}\)
4. \(8\times 10^6~\text{m/s}\)
An electron is accelerated from rest through a potential difference of \(V\) volt. If the de Broglie wavelength of an electron is \(1.227\times10^{-2}~\text{nm}\). what will be its potential difference?
1. \(10^{2}~\text{V}\)
2. \(10^{3}~\text{V}\)
3. \(10^{4}~\text{V}\)
4. \(10^{5}~\text{V}\)
1. \(0.25~\mathring{A}\)
2. \(0.5~\mathring{A}\)
3. \(1.5~\mathring{A}\)
4. \(2~\mathring{A}\)
In an experiment of the photoelectric effect, the wavelength of incident radiation is . The wavelength of incident radiation is reduced to rd of initial value and the maximum kinetic energy of photoelectron is observed to be n times the previous value. What will be the threshold wavelength for the metal plate?
| 1. | \(\dfrac{n-1}{n-3} \lambda \) | 2. | \(\dfrac{n}{n-3} \lambda \) |
| 3. | \(\dfrac{n-3}{n-1} \lambda \) | 4. | \(\dfrac{n+1}{n-3} \lambda\) |
| 1. | \(1.00\) | 2. | \(1.02\) |
| 3. | \(1.04\) | 4. | \(0.98\) |
| 1. | decrease by \(2\) times |
| 2. | decrease by \(4\) times |
| 3. | increase by \(4\) times |
| 4. | increase by \(2\) times |
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