Dual Nature of Radiation and Matter · Question 57

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

The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of the incident radiation for which the stopping potential is 5 V lies in the

1. infrared region
2. X-ray region
3. Ultraviolet region
4. Visible region

A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of 3 106 m s-1. The velocity of the particle is

1. 3 10-31 m s-1
2. 2.7 10-21 m s-1
3. 2.7 10-18 m s-1
4. 9 10-2 m s-1

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.