Advertisements
Advertisements
प्रश्न
Radiation of wavelength 4500 Å is incident on a metal having work function 2.0 eV. Due to the presence of a magnetic field B, the most energetic photoelectrons emitted in a direction perpendicular to the field move along a circular path of radius 20 cm. What is the value of the magnetic field B?
Advertisements
उत्तर
Data: λ = 4500 Å = 4.5 × 10-7 m,
Φ = 2.0 eV = 2 × 1.6 × 10-19 J = 3.2 × 10-19 J
h = 6.63 × 10-34 J.s, c = 3 × 108 m/s,
r = 20 cm = 0.2 m, e = 1.6 × 10-19 C, m = 9.1 × 10-31 kg
`1/2 "mv"_"max"^2 ("KE"_"max") = "hc"/lambda -* phi`
`= ((6.63 xx 10^-34)(3 xx 10^8))/(4.5 xx 10^-7) - 3.2 xx 10^-19`
= 4.42 × 10-19 - 3.2 × 10-19
= 1.22 × 10-19 J
∴ `"v"_"max" = sqrt(2/"m" "KE"_"max") = sqrt((2 xx 1.22 xx 10^-19)/(9.1 xx 10^-31))`
`= sqrt(0.2681 xx 10^12) = 5.178 xx 10^5` m/s
Now, centripetal force, `("mv"_"max"^2)/"r"` = magnetic force, Bevmax
∴ B = `("mv"_"max")/"re" = ((9.1 xx 10^-31)(5.178 xx 10^5))/((0.2)(1.6 xx 10^-19))`
= 1.472 × 10-5 T
APPEARS IN
संबंधित प्रश्न
Can microwaves be used in the experiment on photoelectric effect?
Explain the inverse linear dependence of stopping potential on the incident wavelength in a photoelectric effect experiment.
The electrons are emitted in the photoelectric effect from a metal surface.
Planck's constant is 6.6 × 10-34 Js. The momentum of each photon is given radiation Is 3.3 × 10-29 kg/s. The λ of radiation is ______.
Find the energy of photon which have momentum 2 × 10-16 gm-cm/sec.
With the help of a circuit diagram describe the experiment to study the characteristics of the photoelectric effect. Hence discuss any 2 characteristics of the photoelectric effect.
The maximum velocity of the photoelectron emitted by the metal surface is v. Charge and the mass of the photoelectron is denoted by e and m, respectively. The stopping potential in volt is ______.
The maximum velocity of photoelectron emitted is 4.8 m/s. If the e/m ratio of the electron is 1.76 × 1011 C/kg, then stopping potential is given by ______
The ratio of energies of photons produced due to transition of electron of hydrogen atom from its (i) second to first energy level and (ii) highest energy level to second level is respectively.
An important spectral emission line has a wavelength of 21 cm. The corresponding photon energy is (h = 6.62 x 10-34 Js, c = 3 x 108 m/s) ____________.
Light of wavelength `lambda` strikes a photo-sensitive surface and electrons are ejected with kinetic energy E. If the kinetic energy is to be increased to 2E, the wavelength must be changed to `lambda'` where ____________.
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)
The photo electric effect to take place for a metal, the minimum frequency required is 5.792 × 1014 Hz. A light of wavelength 6000 Å is incident on that metal surface. What is the corresponding frequency of light and will there be photoelectric emissions? [velocity of light = 3 × 108 m/s]
Light of different frequencies, whose photons have energies 3 eV and 18 eV respectively, successively illuminate a metal of work function 2 eV. The ratio of the maximum speeds of the emitted electrons will be ______.
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) ____________.
A light of wavelength '`lambda`' and intensity 'I' falls on photosensitive material. If 'N' photoelectrons are emitted, each with kinetic energy E, then ____________.
When a metal with work function 0.6 eV is illuminated with light of energy 2 eV, the stopping potential will be ____________.
A light of frequency 'v' is incident on the metal surface whose threshold frequency is 'v0'. If v = v0, then [c = speed of light in medium] ____________.
When the work function of a metal increases, maximum kinetic energy of emitted photoelectrons ____________.
Which one of the following graphs represents the variation of photoelectric current (i) with intensity (I) of the incident light?
Is it always necessary to use red light to get a photoelectric effect?
In a photoelectric experiment, ultraviolet light of wavelength 280 nm is used with a lithium cathode having work function Φ = 2.5 eV. If the wavelength of incident light is switched to 400 nm, find out the change in the stopping potential.
(h = 6.63 × 10-34 Js, c = 3 × 108 ms-1)
The radiation emitted, when an electron jumps from n = 3 to n = 2 orbit is a hydrogen atom, falls on a metal to produce photoelectron. The electrons from the metal surface with maximum kinetic energy are made to move perpendicular to a magnetic field of `1/320`T in a radius of 10-3m. Find the 320 work function of metal:
The maximum kinetic energy of the photoelectrons ejected will be ______ eV when the light of wavelength 350 nm is incident on a cesium surface. The work function of cesium = 1.9 eV.
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.
