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प्रश्न
Define photoelectric effect.
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उत्तर
The phenomenon of emission of electrons from a metal surface when radiation of appropriate frequency is incident on it is known as the photoelectric effect.
संबंधित प्रश्न
If the frequency of incident light falling on a photosensitive material is doubled, then the kinetic energy of the emitted photoelectron will be ______.
Choose the correct option.
Polychromatic (containing many different frequencies) radiation is used in an experiment on the photoelectric effect. The stopping potential ______.
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 |
The threshold wavelength of tungsten is 2.76 x 10-5 cm.
(a) Explain why no photoelectrons are emitted when the wavelength is more than 2.76 x 10-5 cm.
(b) What will be the maximum kinetic energy of electrons ejected in each of the following cases
(i) if ultraviolet radiation of wavelength λ = 1.80 × 10-5 cm and
(ii) radiation of frequency 4 x 1015 Hz is made incident on the tungsten surface?
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 |
Find the kinetic energy of the emitted electron, if in photoelectric effect energy of incident Photon is 4 eV and work function is 2.4 eV.
With the help of a circuit diagram describing an experiment to study the photoelectric effect.
State Einstein’s photoelectric equation. Explain all characteristics of the photoelectric effect, on the basis of Einstein’s photoelectric equation.
Which one of the following is TRUE in photoelectric emission?
When a photon enters glass from air, which one of the following quantity does not change?
If the maximum kinetic energy of emitted electrons in photoelectric effect is 3.2 × 10-19 J and the work-function for metal is 6.63 × 10-19 J, then stopping potential and threshold wavelength respectively are
[Planck's constant, h = 6.63 × 1034 J-s]
[Velocity of light, c = 3 × 108 `"m"/"s"`]
[Charge on electron= 1.6 × 10-19 C]
The work function of a metal is 1.6 x 10-19 J. When the metal surface is illuminated by the light of wavelength 6400 Å, then the maximum kinetic energy of emitted photo-electrons will be (Planck's constant h = 6.4 x 10-34 Js) ____________.
Threshold wavelength for lithium metal is 6250 Å. For photoemission, the wavelength of the incident light must be ______.
In photoelectric effect, for a light of different intensities but of same frequency, the stopping potential for a given metal is ____________.
When wavelength of incident radiation on the metal surface is reduced from 'λ1' to 'λ2', the kinetic energy of emitted photoelectrons is tripled. The work function of the metal is ______.
(h = Planck's constant, c =velocity of light)
When light of wavelength 'λ' is incident on a photosensitive surface, the stopping potential is 'V'. When light of wavelength '3λ' is incident on the same surface, the stopping potential is `"V"/6`. Threshold wavelength for the surface is _______.
Following graphs show the variation of stopping potential corresponding to the frequency of incident radiation (F) for a given metal. The correct variation is shown in graph (v0 = Threshold frequency).
The photon of frequency vis incident on a metal surface whose threshold frequency is v0. The kinetic energy of the emitted photoelectrons will be ______.
When a photosensitive surface is irradiated by lights of wavelengths `lambda_1` and `lambda_2`, kinetic energies of emitted photoelectrons are E1 and E2 respectively. The work function of the photosensitive surface is ____________.
A metal surface having work function 'w0' emits photoelectrons when photons of energy 'E' are incident on it. The electron enters the uniform magnetic field (B) in perpendicular direction and moves in circular path of radius 'r'. Then 'r' is equal to (m and e be the mass and charge of electron respectively) ____________.
The wavelength of light incident on a metal surface is reduced from 300 nm to 200 nm (both are less than threshold wavelength). What is the change in the stopping potential for photoelectrons emitted from the surface will be ______ V. (Take h = 6.6 × 10-34 J-s)
For a given photosensitive material and frequency (> threshold frequency) of incident radiation, the photoelectric current varies with the intensity of incident light as:
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 ______.
The following graphs show the variation of stopping potential corresponding to the frequency of incident radiation (ν) for a given metal. The correct variation is shown in graph [ν0 = threshold frequency].
|
(A) |
(B) |
|
(C) |
(D) |
Give Einstein's explanation of the photoelectric effect.
Draw a neat labelled diagram of photo-current as a function of accelerating potential for fixed incident intensity but different incident frequencies for the same emitter material.
