Dual Nature of Radiation and Matter · Question 62

Monochromatic light of frequency 6.0 1014 Hz is produced by a laser. The power emitted is 2 10-3 W. The number of photons emitted, on the average, by the source per second is

1. 5 1016
2. 5 1017
3. 5 1014
4. 5 1015

A 5 watt source emits monochromatic light of wavelength 5000 A. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of

1. 8
2. 16
3. 2
4. 4

A photocell employs photoelectric effect to convert

1. change in the frequency of light into a change in the electric current
2. change in the frequency of light into a change in electric voltage
3. change in the intensity of illumination into a change in photoelectric current
4. change in the intensity of illumination into a change in the work function of the photocathode.

When photons of energy h fall on an aluminium plate (of work function E0), photoelectrons of maximum kinetic energy K are ejected. If the frequency of radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be

1. K + h
2. K + E0
3. 2K
4. K.

In a discharge tube ionization of enclosed gas is produced due to collisions between

1. neutral gas atoms/molecules
2. positive ions and neutral atoms/molecules
3. negative electrons and neutral atoms/molecules
4. photons and neutral atoms/molecules.

The momentum of a photon of energy 1 MeV in kg m/s will be

1. 5 10-22
2. 0.33 106
3. 7 10-24
4. 10-22

The work functions for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einstein's equation the metals which will emit photoelectrons for a radiation of wavelength 4100 A is/are

1. A only
2. A and B only
3. all the three metals
4. none

A photosensitive metallic surface has work function, h 0. If photons of energy 2h 0 fall on this surface, the electrons come out with a maximum velocity of 4 106 m/s. When the photon energy is increased to 5h 0, then maximum velocity of photoelectrons will be

1. 2 107 m/s
2. 2 106 m/s
3. 8 106 m/s
4. 8 105 m/s

According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is

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

A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then

1. each emitted electron carries one quarter of the initial energy
2. number of electrons emitted is half the initial number
3. each emitted electron carries half the initial energy
4. number of electrons emitted is a quarter of the initial number