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प्रश्न
It is observed in an experiment on the photoelectric effect that an increase in the intensity of the incident radiation does not change the maximum kinetic energy of the electrons. Where does the extra energy of the incident radiation go? Is it lost? State your answer with explanatory reasoning.
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उत्तर
Electrons are emitted when electromagnetic radiation with a frequency greater than the threshold frequency is incident on a metal surface. It has been noticed that not every incident photon is capable of realising an electron. In fact, the number of electrons emitted per second is far less than the number of photons incident per second. Photons that are ineffective in the liberation of electrons are reflected (or scattered) or absorbed, causing the temperature of the metal surface to rise. The maximum kinetic energy of a photoelectron is determined by the frequency of incident radiation and the metal's threshold frequency. It has nothing to do with the intensity of the incident radiation. As the intensity increases, so does the number of electrons emitted per second.
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संबंधित प्रश्न
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Explain the inverse linear dependence of stopping potential on the incident wavelength in a photoelectric effect experiment.
Using the values of work function given in the following table, tell which metal will require the highest frequency of incident radiation to generate photocurrent.
Typical values of work function for some common metals
| Metal | Work function (in eV) |
| Potassium | 2.3 |
| Sodium | 2.4 |
| Calcium | 2.9 |
| Zinc | 3.6 |
| Silver | 4.3 |
| Aluminium | 4.3 |
| Tungsten | 4.5 |
| Copper | 4.7 |
| Nickel | 5.0 |
| Gold | 5.1 |
Given the following data for incident wavelength and the stopping potential obtained from an experiment on the photoelectric effect, estimate the value of Planck's constant and the work function of the cathode material. What is the threshold frequency and corresponding wavelength? What is the most likely metal used for emitter?
| Incident wavelength (in Å) | 2536 | 3650 |
| Stopping potential (in V) |
1.95 | 0.5 |
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(A) |
(B) |
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(C) |
(D) |
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