CUET Physics MCQs Unit VII Dual Nature of Matter and Radiation

Question : Which of the following metals is not sensitive to visible light?
(a) Caesium
(b) Sodium
(c) Rubidium
(d) Cadmium

Answer: D

Question : Photoelectric effect can be explained by
(a) wave theory of light
(b) Bohr’s theory
(c) quantum theory of light
(d) corpuscular theory of light

Answer: D

Question : Electron volt (ev) is the unit of
(a) energy 
(b) potential
(c) current 
(d) charge

Answer: A

Question : A strong argument for the particle nature of cathode rays is that they
(a) produce fluoroscence
(b) travel through vacuum
(c) get deflected by electric and magnetic fields
(d) cast shadow

Answer: C 

Question : Photoelectric emmision occurs only when the incident light has more than a certain minimum
(a) power
(b) wavelength
(c) intensity
(d) frequency

Answer: D

Question : A discharge takes place between the two electrodes on applying the electric field to the gas in the discharge tube. The cause of this fluorescence was attributed to
(a) the radiations which appeared to be coming from the anode
(b) the radiation which appeared to be coming from the cathode
(c) the protons coming from the cathode
(d) the protons coming from the anode

Answer: B

Question : Particle like behavior of light arises from the fact that each quanta of light has definite ...X... and a fixed value of ...Y.. just like a particle, Here, X and Y refer to
(a) frequency, energy
(b) shape, volume
(c) energy, frequency
(d) energy, momentum

Answer: D

Question : The theory of quantisation of electric charge was given by
(a) William Crookes
(b) J. J. Thomson
(c) R.A. Millikan
(d) Wilhelm Hallwachs

Answer: C 

Question : The photoelectric current does not depend upon the
(i) frequency of incident light
(ii) work function of the metal
(iii) stopping potential
(iv) intensity of incident light
(a) (i) and (iv) only
(b) (ii) and (iii) only
(c) (iii) only 
(d) (ii) only

Answer: C 

Question : In Einstein’s picture of Photoelectric emission, the photoelectric emission does not take place by
(a) continuous emission of energy from radiation
(b) continuous absorption of energy from radiation
(c) discrete absorption of energy from radiation
(d) discrete emission of energy from radiation

Answer: B

Question : In a photon-particle collision, the quantity that does not remain conserved is
(a) total energy 
(b) total momentum
(c) number of photons 
(d) None of these

Answer: C 

Question : The momentum of a photon of wavelength λ is
(a) hλ 
(b) h/λ 
(c) λ/h 
(d) h/cλ

Answer: B

Question : Light of a particular frequency υ is incident on a metal surface. When the intensity of incident radiation is increased, the photoelectric current
(a) decreases
(b) increases
(c) remains unchanged
(d) sometimes increases and sometimes decreases

Answer: B

Question : The maximum energy of electrons released in a photocell is independent of
(a) the frequency of the incident light
(b) the intensity of the incident light
(c) the nature of the cathode
(d) All of the above

Answer: C 

Question : Photoelectric effect is the phenomenon in which
(a) photons come out of a metal when it is hit by a beam of electrons.
(b) photons come out of the nucleus of an atom under the action of an electric field.
(c) electrons come out of a metal with a constant velocity
(d) which depends on the frequency and intensity of incident light wave.

Answer: D

Question : Einstein’s photoelectric equation is Ek : hν - Φ . In this equation Ek refers to
(a) kinetic energy of all the emitted electrons
(b) mean kinetic energy of emitted electrons
(c) maximum kinetic energy of emitted electrons
(d) minimum kinetic energy of emitted electrons

Answer: C 

Question : ____ and _____ led to understanding of atomic structures.
(i) Fresnel diffraction
(ii) cathode rays
(iii) X-rays
(iv) electrons
(a) (i) and (ii) 
(b) (ii) and (iii)
(c) (i) and (iv) 
(d) (iii) and (iv)

Answer: D

Question: In a photoelectric experiment the stopping potential for the incident light of wavelength 4000Å is 2 volt. If the wavelength be changed to 3000 Å, the stopping potential will be
(a) 2 V
(b) zero
(c) less than 2 V
(d) more than 2 V

Answer: D

Question: Radiations of two photon’s energy, twice and ten times the work function of metal are incident on the metal surface successsively. The ratio of maximum velocities of photoelectrons emitted in two cases is
(a) 1 : 2
(b) 1 : 3
(c) 1 : 4
(d) 1 : 1

Answer: B

Question : When the speed of electrons increase, then the value of its specific charge
(a) increases
(b) decreases
(c) ramains unchanged
(d) increases upto some velocity

Answer: B

Question : When light is incident on a metal surface the maximum kinetic energy of emitted electrons
(a) vary with intensity of light
(b) vary with frequency of light
(c) vary with speed of light
(d) vary irregularly

Answer: B

Question : In which of the following, emission of electrons does not take place?
(a) Thermionic emission
(b) X-rays emission
(c) Photoelectric emission
(d) Secondary emission

Answer: B

Question : In photoelectric effect, electrons are ejected from metals,if the incident light has a certain minimum
(a) wavelength
(b) frequency
(c) amplitude
(d) angle of incidence

Answer: B

Question : The wave theory of light does not explain
(a) polarisation
(b) diffraction
(c) photocurrent
(d) interference

Answer: C 

Question : Electrically, photons are
(a) positively charged
(b) negatively charged
(c) neutral
(d) strongly charged, may be positive or negative

Answer: C 

Question : The photoelectrons emitted from a metal surface are such that their velocity
(a) is zero for all
(b) is same for all
(c) lies between zero and infinity
(d) lies between zero and a finite maximum

Answer: D

Question : The photoelectric effect can be understood on the basis of
(a) wave theroy of light only
(b) electromagnetic theory of light only
(c) quantum theory of light only
(d) None of these

Answer: C 

Question : The minimum energy required to eject an electron, from the metal surface is called
(a) atomic energy 
(b) mechanical energy
(c) electrical energy 
(d) workfunction

Answer: B

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

Answer: D

Question : According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal Vs the frequency of the incident radiation gives as straight the whose slope
(a) depends both on the intensity of the radiation and the metal used
(b) depends on the intensity of the radiation
(c) depends on the nature of the metal used
(d) is the same for the all metals and independent of the intensity of the radiation

Answer: D

Question: A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 2 m away, the number of electrons emitted by photocathode are reduced by a factor of
(a) 1/8
(b) 1/16
(c) 1/2
(d) 1/4

Answer: D

Question: In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by
(a) increasing the potential difference between the anode and filament
(b) increasing the filament current
(c) decreasing the filament current
(d) decreasing the potential difference between the anode and filament

Answer: A

Question: When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is
(a) 0.65 eV
(b) 1.0 eV
(c) 1.3 eV
(d) 1.5 eV

Answer: B

Question : The photoelectrons emitted from a metal surface are such that their velocity
(a) is zero for all
(b) is same for all
(c) lies between zero and infinity
(d) lies between zero and a finite maximum

Answer: D

Question : The presently accepted value of charge/mass (e/m)is
(a) 1.66 x 10–19 c/kg
(b) 9.1 x 1011 c/kg
(c) 1.76 x 1011 c/kg
(d) 9.1 x 1019 c/kg

Answer: C 

Question : The work-function of a metal is
(a) the minimum current required to take out electron from the metal surface
(b) the maximum frequency required to take out electron from the metal surface
(c) the minimum amount of energy required to take out the electron from the metal surface
(d) None of these

Answer: C 

Question : The stopping potential is directly related to
(a) the work function of the metal
(b) intensity of incident radiation
(c) the saturation current for the given frequency
(d) the kinetic energy gained by the photoelectrons

Answer: D

Question : It is essential to consider light as a stream of photons to explain
(a) diffraction of light
(b) refraction of light
(c) photoelectric effect
(d) reflection of light

Answer: C 

Question : The photoelectric effect is based on the law of conservationof
(a) momentum 
(b) energy
(c) angular momentum 
(d) mass

Answer: B

Question : The work function for photoelectric effect
(a) is different for different metals
(b) is same for all metals
(c) depends upon the intensity of incident light
(d) depends upon the frequency of incident light

Answer: A

Question : The energy of photon of wavelength λ is
(a) cλ/h 
(b) hλ/c
(c) hc/λ 
(d) c/hλ

Answer: C 

Question: Light from a hydrogen discharge tube is incident on the cathode of a photoelectric cell, the work function of the cathode surface is 4.2 eV. In order to reduce the photocurrent to zero the voltage of the anode relative to the cathode must be made
(a) – 4.2 V
(b) – 9.4 V
(c) – 17.8 V
(d) + 9.4 V

Answer: B

Question : A photoelectric cell is a device which
(a) converts light into electricity
(b) converts electricity into light
(c) stores light
(d) stores electricity

Answer: A

Question : Which of the following when falls on a metal will emit photoelectrons ?
(a) UV radiations
(b) Infrared radiation
(c ) Radio waves
(d) Microwaves

Answer: A

Question : A photosensitive substance emits _____when illuminated by light.
(a) only protons
(b) only neutrons
(c) electrons and protons
(d) only electrons

Answer: D

Question : Of the following properties, the photon does not possess
(a) rest mass 
(b) momentum
(c) energy 
(d) frequency

Answer: A

Question : Einstein’s photoelectric equation states that hν : W0 + Ek. In this equatin, Ek refers to the
(a) kinetic energy of all the emitted electrons
(b) mean kinetic energy of the emitted electrons
(c) maximum kinetic energy of the emitted electrons
(d) minimum kinetic energy of the emitted electrons

Answer: C 

Question : A photo sensitive metal is not emitting photo-electrons when irradiated. It will do so when threshold is crossed. To cross the threshold we need to increase
(a) intensity 
(b) frequency
(c) wavelength 
(d) None of these

Answer: B

Question: When the minimum wavelength of X-rays is 2Å then the applied potential difference between cathode and anticathode will be
(a) 6.2 kV
(b) 2.48 kV
(c) 24.8 kV
(d) 62 kV

Answer: A

Question : In which of the following, emission of electrons does not take place?
(a) Thermionic emission
(b) X-rays emission
(c) Photoelectric emission
(d) Secondary emission

Answer: B

Question : The wave nature of light was established by
(i) Maxwell’s equations (ii) Fraunhoffer’s lines
(iii) Hertz experiment (iv) Einstein’s theory
(a) (i) and (ii) only 
(b) (ii) and (iv) only
(c) (i) and (iii) only 
(d) (iii) and (iv) only

Answer: C 

Question : The particle nature of light is not confirmed by
(a) photoelectric effect
(b) scattering of X-rays by electrons
(c) diffraction of electrons
(d) compton effect

Answer: C 

Question : A photoelectric cell converts
(a) light energy into heat energy
(b) light energy to sound energy
(c) light energy into electric energy
(d) electric energy into light energy

Answer: C 

Question : In Heinrich Hertz’s experiment on the production of electromagnetic waves by means of spark discharge, it was observed that high voltage sparks across the detector loop were _____ when the emitter plate was illuminated by _____ light
(a) degraded, infra-red 
(b) degraded, ultraviolet
(c) enhanced, ultraviolet 
(d) enhanced, infra-red.

Answer: C 

Question: The work functions of Silver and Sodium are 4.6 and 2.3 eV, respectively. The ratio of the slope of the stopping potential versus frequency plot for Silver to that of Sodium is
(a) 1
(b) 2
(c) 4
(d) zero

Answer: A

Question : Photoelectric effect is the phenomenon in which
(a) photons come out of a metal when it is hit by a beam of electrons.
(b) photons come out of the nucleus of an atom under the action of an electric field.
(c) electrons come out of a metal with a constant velocity
(d) which depends on the frequency and intensity of incident light wave.

Answer: D

Question : The work function of a metal is independent of
(i) nature of the surface of the metal
(ii) dimensions of the metal
(iii) properties of the metal
(iv) abundance of the metal
(a) (i) only
(b) (i) and (iii)
(c) (ii) and (iii) 
(d) (ii) and (iv)

Answer: D

Question : Photoelectric effect was discovered by
(a) Hertz
(b) Hallwachs
(c) Lenard
(d) Millikan

Answer: A

Question : A photon will have less energy, if its
(a) amplitude is higher
(b) frequency is higher
(c) wavelength is longer
(d) wavelength is shorter

Answer: C 

Question: In Davison-Germer experiment, an electron beam is incident on a crystal. The reflected beam consists of
(a) photons
(b) protons
(c) x-rays
(d) electrons

Answer: D

Question : Cathode ray consists of
(a) photons 
(b) electrons
(c) protons
(d) α-particles

Answer: B

Question : Photons are deflected by
(a) electric field only
(b) magnetic field only
(c) electromagnetic field
(d) None of these

Answer: D

Question : A photoelectric cell is a device which
(a) converts light into electricity
(b) converts electricity into light
(c) stores light
(d) stores electricity

Answer: A

Question : Photoelectric emmision occurs only when the incident light has more than a certain minimum
(a) power
(b) wavelength
(c) intensity
(d) frequency

Answer: D

Question : When light is incident on a metal surface the maximum kinetic energy of emitted electrons
(a) vary with intensity of light
(b) vary with frequency of light
(c) vary with speed of light
(d) vary irregularly

Answer: B

Question : In an electron gun the control grid is given a negative potential relative to cathode in order to
(a) decelerate electrons
(b) repel electrons and thus to control the number of electrons passing through it
(c) to select electrons of same velocity and to converge them along the axis.
(d) to decrease the kinetic energy of electrons

Answer: B

Question : Photoelectric effect shows
(a) wave like behaviour of light
(b) paritcle like behaviour of light
(c) both wavelike and paticle like behaviour
(d) neither wave like nor particle like behaviour of light

Answer: B

Question: Sodium and copper have work functions 2.3 eV and 4.5 eV respectively. Then the ratio of the wavelengths is nearest to
(a) 1 : 2
(b) 4 : 1
(c) 2 : 1
(d) 1 : 4

Answer: C 

Question : The maximum energy of electrons released in a photocell is independent of
(a) the frequency of the incident light
(b) the intensity of the incident light
(c) the nature of the cathode
(d) All of the above

Answer: C 

Question : In the photoeletric effect, electrons are emitted
(a) at a rate that is proportional to the amplitude of the incident radiation
(b) with a maximum velocity proportional to the frequency of the incident radiation
(c) at a rate that is independent of the emitter
(d) only if the frequency of the incident radiations is above a certain threshold value

Answer: D