Advertisements
Advertisements
प्रश्न
Photocurrent recorded in the microammeter in an experimental setup of the photoelectric effect vanishes when the retarding potential is more than 0.8 V if the wavelength of incident radiation is 4950 Å. If the source of incident radiation is changed, the stopping potential turns out to be 1.2 V. Find the work function of the cathode material and the wavelength of the second source.
Advertisements
उत्तर
Data: VO = 0.8 V, λ = 4950 Å = 4.950 x 10-7 m, `"V"_"O"'` = 1.2 V, h = 6.63 × 10-34 J.s, c = 3 × 108 m/s
1. `"V"_"O""e" = "hv" - phi = "hc"/lambda - phi`
∴ The work function of the cathode material,
`phi = "hc"/lambda - "V"_"O""e"`
`= ((6.63 xx 10^-34)(3 xx 10^8))/(4.950 xx 10^-7) - (0.8)(1.6 xx 10^-19)`
= 4.018 × 10-19 - 1.28 × 10-19
= 2.738 × 10-19 J
`= (2.738 xx 10^-19 "J")/(1.6 xx 10^-19 "J"//"eV")`
= 1.711 eV
2. `"V"_"O"'"e" = "hc"/(lambda') - phi`
∴ `"hc"/(lambda') = "V"_"O"'"e" + phi`
∴ The wavelength of the second source,
`lambda' = "hc"/("V"_"O"'"e" + phi)`
`= ((6.63 xx 10^-34)(3 xx 10^8))/((1.2)(1.6 xx 10^-19) + 2.738 xx 10^-19)`
`= (19.89 xx 10^-26)/(4.658 xx 10^-19)`
= 4.270 × 10-7 m
= 4270 Å
APPEARS IN
संबंधित प्रश्न
Can microwaves be used in the experiment on photoelectric effect?
As the intensity of incident light increases ______
The maximum kinetic energy of the photoelectrons depends only on ______
The minimum frequency for photoelectric effect on metal is 7 × 1014 Hz, Find the work function of the metal.
If the total energy of radiation of frequency 1014 Hz is 6.63 J, Calculate the number of photons in the radiation.
What is the photoelectric effect? Define stopping potential and photoelectric work function.
The work function of a surface is 3.1 eV. A photon of frequency 1 × 1015 Hz. Is an incident on it. Calculate the incident wavelength is photoelectric emission occurs or not.
The following graph shows the stopping potential V0 versus frequency v for photoelectric emission from two metals A and B. The slope of each of the lines gives ______
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]
A metal surface is illuminated by light of given intensity and frequency to cause photoemission. If the intensity of illumination is reduced to one-fourth of its original value then the maximum KE of the emitted photoelectrons would be ______.
Photoelectrons emitted from a metallic surface are initially ____________.
A metal surface is illuminated by photons of energy 5 eV and 2.5 eV respectively. The ratio of their wavelengths is ____________.
When certain metal surface is illuminated with a light of wavelength A., the stopping potential is V, When the same surface is illuminated by light of wavelength 2λ, the stopping potential is `("V"/3)`. The threshold wavelength for the surface is ______.
In photoelectric effect, graph of saturation current versus frequency of light is plotted. The nature of the graph will be ____________.
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)
Photoelectrons are emitted from a photosensitive surface for the light of wavelengths λ1 = 360 nm and λ2 = 600 nm. What is the ratio of work functions for lights of wavelength 'λ1' to 'λ2'?
The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photo-emission from this substance is approximately (h = 6.63 × 10-34 Js)[1eV = 1.6 × 10-19 J]
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 work function of a photosensitive material is 4.0 eV. The longest wavelength of light that can cause photon emission from the substance is (approximately) ____________.
Which one of the following statements ts INCORRECT for stopping potential in photoelectric emission?
The radiations of energies 1 eV and 2.5 eV are incident on a metal surface having work function 0.5 eV. The ratio of the maximum velocities of the emitted photo-electrons is ____________.
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) ____________.
Photoelectrons are observed to just emit out of a material surface when the light of 620 nm falls on it with the intensity of 100 W m-2. If the light of wavelength 400 nm is incident on the same material with an intensity of 1 W m-2, what would be the minimum reverse potential needed to stop the outflow of the electrons?
In a photocell, frequency of incident radiation is increased by keeping other factors constant (v > v0), the stopping potential ______.
When monochromatic light of frequency v1 falls on a metal surface, the stopping potential required is found to be V1. If the radiation of frequency v2 is incident on the surface, the stopping potential required V2 is ______. (v2 > v1)
Define photoelectric work function of a metal.
Light of wavelength 'λ' falls on a metal having work function \[\frac {hc}{λ_0}\]. Photoelectric effect will take place only if (λ0 is the threshold wavelength) ______.
