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: Photoelectric current increases

Question:

• a) 1.5 × 10²⁰
• b) 6 × 10¹⁸
• c) 3 × 10¹⁹
• d) 62 × 10²⁰

Answer: 1.5 × 10²⁰

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: Four times

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: 6.63 × 10^–34 J s

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 and B only

Question:

• a) 8 × 10⁶ m/s
• b) 8 × 10⁵ m/s
• c) 2 × 10⁶ m/s
• d) 2 × 10⁷ m/s

Answer: 8 × 10⁶ m/s

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: Change in the intensity of illumination into a change in photoelectric current

Question:

• a)

  

• b)

  

• c) 2KK
• d) K

Answer:

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: 4

Question:

• a) Intensity of light
• b)

  

• c)

  

• d)

  

Answer: Intensity of light

Question:

• a) Curves (a) and (b) represent incident radiations of same frequency but of different intensities
• b) Curves (b) and (c) represent incident radiations of different frequencies and different intensities
• c) Curves (a) and (b) represent incident radiations of different frequencies and different intensities
• d) Curves (b) and (c) represent incident radiations of same frequency having same intensity

Answer: Curves (a) and (b) represent incident radiations of same frequency but of different intensities

Question:

• a) 1.00
• b) 1.02
• c) 1.04
• d) 0.98

Answer: 1.00

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: –1.2 V

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: 2N and T

More Questions................................... 

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: 1.6 × 10¹⁵ Hz

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: 1.03 V

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: 24 × 10¹⁷

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: Have their speeds varying from zero to a certain maximum value

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: Saturation current will decrease

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: 12.27 Å

Question:

• a) 0.01 Å
• b) 1 Å
• c) 0.1 Å
• d) 10 Å

Answer: 0.01 Å

Question: If the momentum of an electron is changed by P, then the de-Broglie wavelength associated with it changes by 0.5%. The initial momentum of electron will be

• a) 200 P
• b) 400 P
• c) 100 P
• d)

  

Answer: 200 P

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: Decrease by 2 times

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: 2.7 × 10^–18 ms^–1

Question: An electron of mass m, when accelerated through a potential difference V, has de-Broglie wavelength X. The de-Broglie wavelength associated with a proton of mass M accelerated through the same potential difference, will be

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: Momentum

Question:

• a) 1.2 Å
• b) 6.3 Å
• c) 0.12 Å
• d) 24.6 Å

Answer: 1.2 Å

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

• a)

  

• b)

  

• c) Neutron
• d) Proton

Answer:

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: X-rays

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: 1 : 2

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: 3.33 × 10^–29 kg-m/s

Question: An electron and a proton have same kinetic energy. Ratio of their respective de-Broglie wavelength is about

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Dynamic mass of the photon in usual notations is given by

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: de-Broglie wavelength associated with an electron revolving in the nth state of hydrogen atom is directly proportional to

• a) n
• b)

  

• c)

  

• d)

  

Answer: n

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: 0.2 nm

Question: For a proton accelerated through potential difference of one volt, kinetic energy gained in eV is

• a) 1
• b) 1840
• c)

  

• d) 931.5 × 10^–6

Answer: 1

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: Cut-off voltage becomes more than double

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: 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

Question: For an alpha particle, accelerated through a potential difference V, wavelength (in Å) of the associated matter wave is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Which one among the following shows particle nature of light?

• a) Photoelectric effect
• b) Refraction
• c) Interference
• d) Polarization

Answer: Photoelectric effect