Dual Nature of Radiation and Matter

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.

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