Dual Nature of Radiation and Matter

A photoelectric surface is illuminated successively by monochromatic light of wavelength and /2. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface of the material is (h = Planck's constant, c = speed of light)

1. 2hc
2. hc3
3. hc2
4. hc

Light of wavelength 500 nm is incident on a metal with work function 2.28 eV. The de Broglie wavelength of the emitted electron is

1. 2.8 10-9 m
2. 2.8 10-12 m
3. < 2.8 10-10 m
4. < 2.8 10-9 m

Which of the following figures represent the variation of particle momentum and the associated de-Broglie wavelength?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

A certain metallic surface is illuminated with monochromatic light of wavelength, . The stopping potential for photo-electric current for this light is 3V0. If the same surface is illuminated with light of wavelength 2 , the stopping potential is V0. The threshold wavelength for this surface for photo-electric effect is

1. 4
2. 6
3. 6
4. 4

When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is

1. 0.65 eV
2. 1.0 eV
3. 1.3 eV
4. 1.5 eV

If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de Broglie wavelength of the particle is

1. 25
2. 75
3. 60
4. 50

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct ?

1. The angular width of the central maximum will decrease.
2. The angular width of the central maximum will be unaffected.
3. Diffraction pattern is not observed on the screen in the case of electrons.
4. The angular width of the central maximum of the diffraction pattern will increase.

The wavelength e of an electron and p of a photon of same energy E are related by

1. p e
2. p 1 e
3. p e2
4. p e

For photoelectric emission from certain metal the cutoff frequency is . If radiation of frequency 2 impinges on the metal plate, the maximum possible velocity of the emitted electron will be (m is the electron mass)

1. 2h m
2. 2 h m
3. h (2m)
4. h m

A source of light is placed at a distance of 50 cm from a photo cell and the stopping potential is found to be V0. If the distance between the light source and photo cell is made 25 cm, the new stopping potential will be :

1. V0/2
2. V0
3. 4V0
4. 2V0

The de-broglie wavelength of neutrons in thermal equilibrium at temperature T is

1. 3.08 T A
2. 0.308 T A
3. 0.0308 T A
4. 30.8 T A

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 electron will be

1. 200 P
2. 400 P
3. P200
4. 100 P

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 : 4
2. 1 : 2
3. 1 : 1
4. 1 : 5

A 200 W sodium street lamp emits yellow light of wavelength 0.6 . Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is

1. 1.5 1020
2. 6 1018
3. 62 1020
4. 3 1019

Monochromatic radiation emitted when electron in hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57 V. The threshold frequency of the material is

1. 4 1015 Hz
2. 5 1015 Hz
3. 1.6 1015 Hz
4. 2.5 1015 Hz

An -particle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of 0.25 Wb/m2. The de Broglie wavelength associated with the particle will be

1. 1 A
2. 0.1 A
3. 10 A
4. 0.01 A

The threshold frequency for a photosensitive metal is 3.3 1014 Hz. If light of frequency 8.2 1014 Hz is incident on this metal, the cut-off voltage for the photoelectron emission is nearly

1. 1 V
2. 2 V
3. 3 V
4. 5 V

Photoelectric emission occurs only when the incident light has more than a certain minimum

1. power
2. wavelength
3. intensity
4. frequency

Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively illuminate a metallic surface whose work function is 0.5 eV successively. Ratio of maximum speeds of emitted electrons will be

1. 1 : 4
2. 1 : 2
3. 1 : 1
4. 1 : 5

Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV, then the de Broglie wavelength associated with the electrons would

1. increase by 2 times
2. decrease by 2 times
3. decrease by 4 times
4. increase by 4 times

In photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is

1. 1.8 V
2. 1.3 V
3. 0.5 V
4. 2.3 V

In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by

1. increasing the potential difference between the anode and filament
2. increasing the filament current
3. decreasing the filament current
4. decreasing the potential difference between the anode and filament

A radioactive nucleus of mass M emits a photon of frequency and the nucleus recoils. The recoil energy will be

1. Mc2 - h
2. h2 2/2Mc2
3. zero
4. h

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. N and 2T
2. 2N and T
3. 2N and 2T
4. N and T

The electron in the hydrogen atom jumps from excited state (n = 3) to its ground state (n = 1) and the photons thus emitted irradiate a photosensitive material. If the work function of the material is 5.1 eV, the stopping potential is estimated to be (the energy of the electron in nth state En = - 13.6n2 eV)

1. 5.1 V
2. 12.1 V
3. 17.2 V
4. 7 V

A source S1 is producing 1015 photons per second of wavelength 5000 A. Another source S2 is producing 1.02 1015 photons per second of wavelength 5100 A. Then, (power of S2)/(power of S1) is equal to

1. 1.00
2. 1.02
3. 1.04
4. 0.98

The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface, having work function 5.01 eV, when ultraviolet light of 200 nm falls on it, must be

1. 2.4 V
2. -1.2 V
3. -2.4 V
4. 1.2 V

The number of photo electrons emitted for light of a frequency (higher than the threshold frequency 0) is proportional to

1. threshold frequency ( 0)
2. intensity of light
3. frequency of light ( )
4. - 0

The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three different radiations. Which one of the following is a correct statement? [figure]

1. Curves (a) and (b) represent incident radiations of same frequency but of different intensities.
2. Curves (b) and (c) represent incident radiations of different frequencies and different intensities.
3. Curves (b) and (c) represent incident radiations of same frequency having same intensity.
4. Curves (a) and (b) represent incident radiations of different frequencies and different intensities.

Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW. The number of photons arriving per sec. on the average at a target irradiated by this beam is

1. 3 1016
2. 9 1015
3. 3 1019
4. 9 1017