Q. No.
Which among the following verified the wave nature of electrons experimentally?
1. De-Broglie
2. Hertz
3. Einstein
4. Davisson and Germer
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. | \(5~\text{V}\) |
1. \(102\times10^{-3}~\text{nm}\)
2. \(102\times10^{-4}~\text{nm}\)
3. \(102\times10^{-5}~\text{nm}\)
4. \(102\times10^{-2}~\text{nm}\)
What did Einstein prove by the photo-electric effect?
1. \(E = h\nu\)
2. \(K.E = \frac{1}{2}mv^2\)
3. \(E= mc^2\)
4. \(E = \frac{-Rhc^2}{n^2}\)
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. | \(1.2\) eV | 2. | \(0.98\) eV |
| 3. | \(0.45\) eV | 4. | \(0\) eV |
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. \(8\times 10^6~\text{m/s}\)
1. \(\lambda_{ph}< \lambda_e\)
2. \(\lambda_{ph}= \lambda_e\)
3. \(\lambda_{ph}>\lambda_e\)
4. \(\lambda_{ph}= 2\lambda_e\)
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