JEE Physics Dual Nature Of Radiation and Matter MCQs Set C

Question. As the intensity of incident light increases
(a) Photoelectric current increases
(b) Kinetic energy of emitted photoelectrons decreases
(c) Photoelectric current decreases
(d) Kinetic energy of emitted photoelectrons increases

Answer: A

Question. 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
(a) Four times
(b) Two times
(c) One-fourth
(d) Remain same

Answer: A

Question. The value of Planck’s constant is
(a) 6.63 × 10^–34 J s
(b) 6.63 × 10^–34 kg m²
(c) 6.63 × I0^–34 kg m²/s²
(d) 6.63 × 10^–34 J/s

Answer: A

Question. 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 Å is/are
(a) A and B only
(b) All the three metals
(c) A only
(d) None of these

Answer: A

Question. A photocell employs photoelectric effect to convert
(a) Change in the intensity of illumination into a change in photoelectric current
(b) Change in the intensity of illumination into a change in the work function of the photocathode
(c) Change in the frequency of light into a change in electric voltage
(d) Change in the frequency of light into a change in the electric current

Answer: A

Question. A 5 watt source emits monochromatic light of wavelength 5000 Å. 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
(a) 4
(b) 2
(c) 16
(d) 8

Answer: A

Question. 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
(a) –1.2 V
(b) –2.4 V
(c) 2.4 V
(d) 1.2 V

Answer: A

Question. When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectron 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
(a) 2N and T
(b) 2N and 2T
(c) N and T
(d) N and 2T

Answer: A

Question. Monochromatic radiation emitted when electron on 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
(a) 1.6 × 10¹⁵ Hz
(b) 2.5 × 10¹⁵ Hz
(c) 4 × 10¹⁵ Hz
(d) 5 × 10¹⁵ Hz

Answer: A

Question. If in a photoelectric cell, the wavelength of incident light is changed from 4000 Å to 3000 Å then change in stopping potential will be
(a) 1.03 V
(b) 0.66 V
(c) 0.33 V
(d) 0.49 V

Answer: A

Question. Find the number of electrons emitted per second by a 24 W source of monochromatic light of wavelength 6600Å, assuming 3% efficiency for photoelectric effect (take h = 6.6 × 10^–34 Js)
(a) 24 × 10¹⁷
(b) 8 × 10¹⁹
(c) 48 × 10¹⁷
(d) 48 × 10¹⁹

Answer: A

Question. The photo-electrons emitted from a surface of sodium metal are such that they
(a) Have their speeds varying from zero to a certain maximum value
(b) Have the same de-Broglie wavelength
(c) Have the same kinetic energy
(d) All are of the same frequency

Answer: A

Question. In photoelectric effect, if a weak intensity radiation instead of strong intensity of suitable frequency is used then
(a) Saturation current will decrease
(b) Photoelectric effect will not take place
(c) Photoelectric effect will get delayed
(d) Maximum kinetic energy will decrease

Answer: A

Question. The work function of tungsten is 4.50 eV. The wavelength of fastest electron emitted when light whose photon energy is 5.50 eV falls on tungsten surface, is
(a) 12.27 Å
(b) 0.286 Å
(c) 12400 Å
(d) 1.227 Å

Answer: A

Question. 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
(a) Decrease by 2 times
(b) Increase by 4 times
(c) Increase by 2 times
(d) Decrease by 4 times

Answer: A

Question. A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of 3 × 10⁶ ms^–1. The velocity of the particle is (mass of electron = 9.1 × 10^–31 kg)
(a) 2.7 × 10^–18 ms^–1
(b) 9 × 10^–2 ms^–1
(c) 3 × 10^–31 ms^–1
(d) 2.7 × 10^–21 ms^–1

Answer: A

Question. If we consider electrons and photons of same wavelength, then they will have same
(a) Momentum
(b) Angular momentum
(c) Energy
(d) Velocity

Answer: A

Question.  When ultraviolet rays fall on a metal plate then photoelectric effect does not occur, it occurs by
(a) X-rays
(b) Infrared rays
(c) Radiowave
(d) Light wave

Answer: A

Question. A metal surface is illuminated by the photons of energy 5 eV and 2.5 eV respectively. The ratio of their wavelengths is
(a) 1 : 2
(b) 2 : 5
(c) 1 : 4
(d) 1 : 3

Answer: A

Question. If the energy of a photon is 10 eV, then its momentum is
(a) 3.33 × 10^–27 kg-m/s
(b) 3.33 × 10^–29 kg-m/s
(c) 3.33 × 10^–25 kg-m/s
(d) 3.33 × 10^–23 kg-m/s

Answer: B

Question. A proton is accelerated through 225 V. Its de-Broglie wavelength is
(a) 0.2 nm
(b) 0.3 nm
(c) 0.4 nm
(d) 0.1 nm

Answer: A

Question. If frequency of light falling on a photosensitive material doubles
(a) Cut-off voltage becomes more than double
(b) Stopping potential doubles
(c) Saturation photocurrent becomes more than double
(d) Saturation photocurrent doubled

Answer: A

Question. Photoelectrons from metal do not come out with same energy. Most appropriate explanation is
(a) Electrons in metal occupy different energy levels and work function is the minimum energy required for electron in highest level of conduction band to get out of metal
(b) For some electrons, some part of energy gained during inelastic collision with photon is spent in over coming attractive force by nucleus
(c) Work function of a metal is average energy required to pull out electrons
(d) Some electrons loose energy in form of heat

Answer: A

Question. Which one among the following shows particle nature of light?
(a) Photoelectric effect
(b) Refraction
(c) Interference
(d) Polarization

Answer: A