Q. No.If the momentum of an electron is changed by \(p,\) then the de-Broglie wavelength associated with it changes by \(0.5\%.\) The initial momentum of an electron will be:
1. \(400p\)
2. \(\frac{p}{100}\)
3. \(100p\)
4. \(200p\)
1. \(400p\)
2. \(\frac{p}{100}\)
3. \(100p\)
4. \(200p\)
Two radiations of photons energies \(1\) eV and \(2.5\) eV, successively illuminate a photosensitive metallic surface of work function \(0.5\) eV. The ratio of the maximum speeds of the emitted electrons is:
1. \(1:2\)
2. \(1:1\)
3. \(1:5\)
4. \(1:4\)
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 \({E}_0-\phi\) (\(\phi\) is the work function). |
| 4. | electrons can be emitted with any energy, with a maximum \(E_0.\) |
A particle is dropped from a height \(H.\) The de-Broglie wavelength of the particle as a function of height is proportional to:
1. \(H\)
2. \(H^{1/2}\)
3. \(H^{0}\)
4. \(H^{-1/2}\)
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 |
\((h = 6.6\times10^{-34}~\text{J-s})\)
1. \(10^{16}\)
2. \(10^{15}\)
3. \(10^{18}\)
4. \(10^{17}\)
An electromagnetic wave of wavelength \(\lambda\) is incident on a photosensitive surface of negligible work function. If '\(m\)' is the mass of photoelectron emitted from the surface and \(\lambda_d\) is the de-Broglie wavelength, then:
| 1. | \( \lambda=\left(\dfrac{2 {mc}}{{h}}\right) \lambda_{{d}}^2 \) | 2. | \( \lambda=\left(\dfrac{2 {h}}{{mc}}\right) \lambda_{{d}}^2 \) |
| 3. | \( \lambda=\left(\dfrac{2 {m}}{{hc}}\right) \lambda_{{d}}^2\) | 4. | \( \lambda_{{d}}=\left(\dfrac{2 {mc}}{{h}}\right) \lambda^2 \) |
Light of wavelength \(\lambda\) falls on a metal having work function \(\dfrac{hc}{\lambda_0}\). The photoelectric effect will take place only if:
1. \(\lambda \geq\lambda_0\)
2. \(\lambda \geq 2\lambda_0\)
3. \(\lambda \leq\lambda_0\)
4. \(\lambda < \dfrac{\lambda_0}{2}\)
A point source of light is used in a photoelectric effect. If the source is removed farther from the emitting metal, the stopping potential:
| 1. | will increase. |
| 2. | will decrease. |
| 3. | will remain constant. |
| 4. | will either increase or decrease. |
When the intensity of a light source is increased,
| (a) | the number of photons emitted by the source in unit time increases. |
| (b) | the total energy of the photons emitted per unit time increases. |
| (c) | more energetic photons are emitted. |
| (d) | faster photons are emitted. |
Choose the correct option:
| 1. | (a), (b) | 2. | (b), (c) |
| 3. | (c), (d) | 4. | (a), (d) |
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