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. | \(5~\text{V}\) |
When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectrons and their maximum kinetic energy are N and T respectively. If the intensity of radiation is 2I, the number of emitted electrons and their maximum kinetic energy are respectively:
1. 2N and T
2. 2N and 2T
3. N and T
4. N and 2T
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. \(200P\)
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. \(1:4\)
1. | \(V_0 /2\) | 2. | \(V_0 \) |
3. | \(4V_0 \) | 4. | \(2V_0 \) |
The momentum of a photon of energy 1 MeV in kg m/s, will be:
1.
2.
3.
4.
When photons of energy h fall on an aluminium plate (of work function E0), photoelectrons of maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be:
1.
2. 2K
3. K
4. K+h
A photocell employs a photo-electric effect to convert:
1. | change in the frequency of light into a change in electric voltage. |
2. | change in the intensity of illumination into a change in photoelectric current. |
3. | change in the intensity of illumination into a change in the work function of the photocathode. |
4. | change in the frequency of light into a change in the electric current. |
Monochromatic light of frequency 6.0×1014 Hz is produced by a laser. The power emitted is 2×10-3 W. The number of photons emitted, on average, by the source per second is:
1.
2.
3.
4.