Dual Nature of Radiation and Matter

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

J.J. Thomson's cathode-ray tube experiment demonstrated that

1. cathode rays are streams of negatively charged ions
2. all the mass of an atom is essentially in the nucleus
3. the e/m of electrons is much greater than the e/m of protons
4. the e/m ratio of the cathode-ray particles changes when a different gas is placed in the discharge tube

The value of Planck's constant is

1. 6.63 10-34 J/sec.
2. 6.63 10-34 kg-m2/sec2
3. 6.63 10-34 kg-m2
4. 6.63 10-34 J-sec.

If particles are moving with same velocity, then which has maximum de Broglie wavelength?

1. proton
2. -particle
3. neutron
4. -particle

When ultraviolet rays are incident on a metal plate, photoelectric effect does not occur. It occurs by incidence of

1. infrared rays
2. X-rays
3. radio waves
4. microwaves

Which of the following is not the property of cathode rays?

1. It produces heating effect
2. It does not deflect in electric field
3. It casts shadow
4. It produces fluorescence.

Which one among the following shows particle nature of light?

1. photoelectric effect
2. interference
3. refraction
4. polarization

A photo-cell is illuminated by a source of light, which is placed at a distance d from the cell. If the distance becomes d/2, then number of electrons emitted per second, will be

1. remain same
2. four times
3. two times
4. one-fourth

The interplanar distance in a crystal is 2.8 10-8 m. The value of maximum wavelength which can be diffracted is

1. 2.8 10-8 m
2. 5.6 10-8 m
3. 1.4 10-8 m
4. 7.6 10-8 m

By photoelectric effect, Einstein proved

1. E = h
2. K.E. = 12 mv2
3. E = mc2
4. E = -Rhcn2

Who evaluated the mass of electron indirectly with help of charge

1. Thomson
2. Millikan
3. Rutherford
4. Newton