CBSE Class 12 Physics Dual Nature of Matter Assignment

Important Questions for NCERT Class 12 Physics Dual Nature Of Matter And Radiation 

Question. In a photoelectric effect experiment, for radiation with frequency υ₀ with hυ₀ = 8eV, electrons are emitted with energy 2 eV. What is the energy of the electrons emitted for incoming radiation of frequency 1.25 υ₀ ?
(a) 1 eV
(b) 3.25 eV
(c) 4 eV
(d) 9.25 eV.

Answer: C

Question. Einstein’s photoelectric equation is E_k = h_n - 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. 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 which depends on the frequency and intensity of incident light wave.
(d) electons come out of a metal with different velocities not greater than a certain value which depends only on the frequency of the incident light wave and not on its intensity.

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. If E₁, E₂, E₃ are the respective kinetic energies of an electron, an alpha-particle and a proton, each having the same de-Broglie wavelength, then
(a) E₁ > E₃ > E₂
(b) E₂ > E₃ > E₁
(c) E₁ > E₂ > E₃
(d) E₁ = E₂ = E₃

Answer: A

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 and then begins to decrease

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. X-rays are produced in X-ray tube operating at a given accelerating voltage. The wavelength of the continuous X-rays has values from
(a) 0 to ∞
(b) λ_min to ∞, where λ_min > 0
(c) 0 to λ_max, where λ_max < ∞
(d) λ_min to λ_max, where 0 < λ_min <λ_max < ∞

Answer: B

Question. As intensity of incident light increases
(a) photoelectric current increase
(b) K.E. of emitted photoelectron increases
(c) photoelectric current decreases
(d) K.E. of emitted photoelectrons decreases

Answer: A

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

Answer: D

Question. The ratio of de-Broglie wavelengths of proton and a -particle having same kinetic energy is
(a) √2 : 1
(b) 2 √2 : 1
(c) 2 : 1
(d) 4 : 1

Answer: C

Question. White X-rays are called white due to the fact that
(a) they are electromagnetic radiations having nature same as that of white light.
(b) they are produced most abundantly in X ray tubes.
(c) they have a continuous wavelength range.
(d) they can be converted to visible light using coated screens and photographic plates are affected by them just like light.

Answer: C

Question. In case of electrons and photons having the same wavelength. What is same for them?
(a) Energy
(b) Velocity
(c) Momentum
(d) Angular momentum

Answer: C

Question. The energy of a photon of wavelength λ is
(a) hc λ
(b) hc/λ
(c) λ/hc
(d) λh/c

Answer: B

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. 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. A proton and a-particle are accelerated through the same potential difference. The ratio of their de-Broglie wavelength will be
(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) 2 √2 : 1

Answer: D

Question. The stopping potential (V₀) versus frequency (v) plot of a substance is shown in figure, the threshold wavelength is 

(a) 5 × 1014m
(b) 6000 Å
(c) 5000 Å
(d) Cannot be estimated from given data

Answer: B

Question. The de-Broglie wavelength of a proton (mass = 1.6 × 10^–27 kg) accelerated through a potential difference of 1 kV is
(a) 600 A
(b) 0.9 × 10^–12m
(c) 7 Å
(d) 0.9 nm.

Answer: B

Question. An electron is accelerated by a p.d. of 1000 V. Its velocity will be
(a) 3.78 × 10⁷ m/s
(b) 1.89 × 10⁷ m/s
(c) 5.67 × 10⁷ m/s
(d) 0.95 × 10⁷ m/s

Answer: B

Question. If a photon has velocity c and frequency u, then which of the following represents its wavelength?
(a) hν/c²
(b) hν
(c) hν/E
(d) hν/c

Answer :  C

Question. Momentum of photon of wavelength l is
(a) hν/c
(b) zero
(c) hν/C²
(d) hν/c

Answer :  A

Question. The wavelength of a 1 keV photon is 1.24 × 10^–9 m.
What is the frequency of 1 MeV photon?
(a) 1.24 × 10¹⁵
(b) 2.4 × 10²⁰
(c) 1.24 × 10¹⁸
(d) 2.4 × 10²³ 

Answer :  B

Question. A radio transmitter operates at a frequency 880 kHz and a power of 10 kW. The number of photons emitted per second is
(a) 1.72 × 10³¹
(b) 1.327 × 10²⁵
(c) 1.327 × 10³⁷
(d) 1.327 × 10⁴⁵ 

Answer :  A

Question. The momentum of a photon of an electromagnetic radiation is 3.3 ×10^–29 kg m s^–1. What is the frequency of the associated waves? [h = 6.6 × 10^–34 J s ; c = 3 × 10⁸ m s^–1]
(a) 1.5 × 10¹³ Hz
(b) 7.5 × 10¹² Hz
(c) 6 × 10³ Hz
(d) 3 × 10³ Hz 

Answer :  A

Question. The energy of a photon of wavelength l is
(a) hcλ (b) hc/λ
(c) λ/hc
(d) λh/c

Answer :  B

Question. An electron is accelerated from rest through a potential difference of V volt. If the de Broglie wavelength of the electron is 1.227 × 10–2 nm, the potential difference is
(a) 10 V
(b) 10² V
(c) 10³ V
(d) 10⁴ V 

Answer :  A

Question. An electron is accelerated through a potential difference of 10,000 V. Its de Broglie wavelength is, (nearly) (me = 9 × 10^–31 kg)
(a) 12.2 nm
(b) 12.2 × 10^–13 m
(c) 12.2 × 10^–12 m
(d) 12.2 × 10^–14 m

Answer :  C

Question. Light of wavelength 500 nm is incident on a metal with work function 2.28 eV. The de Broglie wavelength of the emitted electron is
(a) ≥ 2.8 × 10^–9 m
(b) ≤ 2.8 × 10^–12 m
(c) < 2.8 × 10^–10 m
(d) < 2.8 × 10^–9 m

Answer :  A

Question. If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de Broglie wavelength of the particle is
(a) 25
(b) 75
(c) 60
(d) 50

Answer :  B

Question. An a-particle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of 0.25 Wb/m2. The de Broglie wavelength associated with the particle will be
(a) 1 Å
(b) 0.1 Å
(c) 10 Å
(d) 0.01 Å 

Answer :  D

Please refer to attached file for CBSE Class 12 Physics Dual Nature of Matter Assignmen