Dual Nature of Matter & Radiation PYQs Set 2 (PDF)

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Mere Teacher · Previous Year Questions JEE Main Physics · Dual Nature of Matter & Radiation · Set 2 (Q31-60)
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31. $The magnetic field of a plane electromagnetic wave is B \to= 3 \times 10^{- 8} sin [200 π (y + ct)] i^T where c = 3 \times 10^{8} ms^{- 1} is the speed of light. The corresponding electric field is$ (1) $E \to= - 9 sin [200 π (y + ct)] k^V / m$ (2) $E \to= 9 sin [200 π (y + ct)] k^V / m$ (3) $E \to= - 10^{- 6} sin [200 π (y + ct)] k^V / m$ (4) $E \to= 3 \times 10^{- 8} sin [200 π (y + ct)] k^V / m$ 32. $An electron of mass m and a photon have same energy E . The ratio of de‐Broglie wavelengths associated with them is (c being velocity of light)$ (1) $c (2 mE)^{\frac{1}{2}}$ (2) $\frac{1}{c} (\frac{2 m}{E})^{\frac{1}{2}}$ (3) $\frac{1}{c} (\frac{E}{2 m})^{\frac{1}{2}}$ (4) $(\frac{E}{2 m})^{\frac{1}{2}}$ 33. $Photoelectrons are emitted with maximum velocity v when light of frequency 3 f incidents on a photosensitive material of work function 2 hf . If the frequency of the incident light is 4.25 f, the maximum velocity of the emitted photoelectrons is (h -- Plank's constant)$ (1) $0.5 v$ (2) $v$ (3) $1.5 v$ (4) $2 v$ 34. $Which of the following has the largest de Broglie wavelength?$ (1) $a bullet of mass 0.02 kg moving with speed 1 km / s$ (2) $a ball of mass 0.06 kg moving with speed 10 m / s$ (3) $a particle of mass 0.01 kg moving with speed 100 m / s$ (4) $a ball of mass 0.03 kg moving with speed 1 m / s$ 35. $An electron beam has a kinetic energy equal to 100 eV Find its wavelength associated with a beam, if mass of electron = 9.1 \times 1 0^{- 31} kg and 1 eV = 1.6 \times 1 0^{- 19} J / eV . (Planck’s constant = 6.6 \times 1 0^{- 34} Js)$ (1) $24.6 Å$ (2) $0.12 Å$ (3) $1.2 Å$ (4) $6.3 Å$ 36. $If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de Broglie wavelength of the particle is$ (1) $25$ (2) $75$ (3) $60$ (4) $50$ 37. $Which of the following figures represent the variation of particle momentum and the associated de-Broglie wavelength?$ (1) (2) (3) (4) 38. $Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R . Assertion A: Number of photons increases with increase in frequency of light. Reason R: Maximum kinetic energy of emitted electrons increases with the frequency of incident radiation. In the light of the above statements, choose the most appropriate answer from the options given below:$ (1) $Both A and R are correct and R is the correct explanation of A .$ (2) $Both A and R are correct and R is NOT the correct explanation of A .$ (3) $A is not correct but R is correct.$ (4) $A is correct but R is not correct.$ 39. $The de-Broglie wavelength of a particle of kinetic energy ' K' is λ; the wavelength of the particle, if its kinetic energy is \frac{K}{4} is$ (1) $\frac{λ}{2}$ (2) $λ$ (3) $4 λ$ (4) $2 λ$ 40. $In photoelectric effect an em-wave is incident on a metal surface and electrons are ejected from the surface. If the work function of the metal is 2.14 eV and stopping potential is 2 V, what is the wavelength of the em-wave? (Given hc = 1242 eV nm where h is the Planck's constant and c is the speed of light in vaccum.)$ (1) $300 nm$ (2) $400 nm$ (3) $600 nm$ (4) $200 nm$ 41. $The photoelectric threshold wavelength for silver is λ_{0} . The energy of the electron ejected from the surface of silver by an incident wavelength λ (λ < λ_{0}) will be$ (1) $hc (λ_{0} - λ)$ (2) $\frac{hc}{λ _{0} - λ}$ (3) $\frac{h}{c} (\frac{λ _{0} - λ}{λ λ _{0}})$ (4) $hc (\frac{λ _{0} - λ}{λ λ _{0}})$ 42. $The de Broglie wavelength of the most energetic photoelectrons emitted from a photosensitive metal of work function φ, when light frequency v incidents on it is λ . Then v = (h - Planck's constant, m - mass of electron)$ (1) $\frac{2 φ}{h} - \frac{h}{m λ ^{2}}$ (2) $\frac{2 φ}{h} + \frac{h}{m λ ^{2}}$ (3) $\frac{φ}{h} + \frac{h}{2 m λ ^{2}}$ (4) $\frac{φ}{h} - \frac{h}{2 m λ ^{2}}$ 43. $Photoelectric work function of a metal is 1 eV Light of wavelength λ = 3000 A^{\circ} falls on it. The photo electrons come out with a maximum velocity$ (1) $10 meters/sec$ (2) $1 0^{2} meters/sec$ (3) $1 0^{4} meters/sec$ (4) $1 0^{6} meters/sec$ 44. $The de-Broglie wavelength of an electron having kinetic energy 100 eV is (Take, h = 4.14 \times 10^{- 15} eV -s, mass of electron (= \frac{0.5 \times 10 ^{6}}{c ^{2}} eV, 1 pm = 10^{- 12} m)$ (1) $150.1 pm$ (2) $124.2 pm$ (3) $115.5 pm$ (4) $120.8 pm$ 45. $When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectrons and their maximum kinetic energy are N and T respectively. If the intensity of radiation is 2 I, the number of emitted electrons and their maximum kinetic energy are respectively$ (1) $N and 2 T$ (2) $2 N and T$ (3) $2 N and 2 T$ (4) $N and T$ 46. $When photons of energy ho fall on an aluminum plate (of work function E_{0}), photoelectrons of maximum kinetic energy K are ejected. If the frequency of radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be$ (1) $K + h ν$ (2) $K + E_{0}$ (3) $2 K$ (4) $K$ 47. $Which one of the following graphs represents the variation of maximum kinetic energy (E_{K}) of the emitted electrons with frequency v in photoelectric effect correctly?$ (1) (2) (3) (4) 48. $The kinetic energy of an electron gets tripled, then the de Broglie wavelength associated with it changes by a factor$ (1) $\frac{1}{3}$ (2) $3$ (3) $\frac{1}{3}$ (4) $3$ 49. $A small object at rest, absorbs a light pulse of power 20 mW and duration 300 ns. Assuming speed of light as 3 x 1 0^{8} m/s. the momentum of the object becomes equal to:$ (1) $0.5 x 1 0^{- 17} kg-m/s$ (2) $2 x 1 0^{- 17} kg-m/s$ (3) $3 x 1 0^{- 17} kg-m/s$ (4) $1 x 1 0^{- 17} kg-m/s$ 50. $The equation λ = \frac{1.227}{x} nm can be used to find the de-Brogli wavelength of an electron. In this equation x stands for: Where, m = mass of electron P = momentum of electron K = Kinetic energy of electron V = Accelerating potential in volts for electron$ (1) $mK$ (2) $P$ (3) $K$ (4) $V$ 51. $An electron of mass m and charge e is accelerated from rest through a potential difference V in vacuum. Its final velocity will be$ (1) $\frac{2 eV}{m}$ (2) $\frac{eV}{m}$ (3) $\frac{eV}{2 m}$ (4) $\frac{eV}{m}$ 52. $The photoelectric threshold wavelength of silver is 3250 \times 10^{- 10} m . The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536 \times 10^{- 10} m is (Given, h = 4.14 \times 10^{- 15} eV -s and c = 3 \times 10^{8} ms^{- 1}) [NEET 2017]$ (1) $\approx 6 \times 10^{5} ms^{- 1}$ (2) $\approx 0.6 \times 10^{7} ms^{- 1}$ (3) $\approx 61 \times 10^{3} ms^{- 1}$ (4) $\approx 0.3 \times 10^{6} ms^{- 1}$ 53. $When light of wavelength λ incidents on a photosensitive material, photoelectrons are emitted. If the wavelength of the incident light is reduced by 50 %, the maximum kinetic energy of the emitted photoelectrons becomes 3 times the initial maximum kinetic energy. The work function of the material is (h - Planck's constant, c -Speed of light in vacuum)$ (1) $\frac{hc}{λ}$ (2) $\frac{hc}{2 λ}$ (3) $\frac{2 hc}{λ}$ (4) $\frac{hc}{3 λ}$ 54. $The threshold frequency of a photosensitive material is v . When photons of frequency 2 v incident on the material, photoelectrons are emitted with a maximum linear momentum P. To get photoelectrons with maximum linear momentum 2 P, the frequency of the incident photons is$ (1) $2 v$ (2) $3 v$ (3) $4 v$ (4) $5 v$ 55. $The additional energy that should be given to an electron to reduce its de-Broglie wavelength from 1 nm to 0.5 nm is$ (1) $2 times the initial kinetic energy$ (2) $3 times the initial kinetic energy$ (3) $0.5 times the initial kinetic energy$ (4) $4 times the initial kinetic energy$ 56. $When the energy of incident radiation is increased by 20 %, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV . The work function of the metal is$ (1) $0.65 eV$ (2) $1.0 eV$ (3) $1.3 eV$ (4) $1.5 eV$ 57. $A photocell employs photoelectric effect to convert$ (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) $change in the intensity of illumination into a change in the work function of the photocathode.$ 58. $The work functions of caesium (Cs), potassium (K) and sodium (Na) are 2.14 eV, 2.30 eV and 2.75 eV, respectively. If incident electromagnetic radiation has an incident energy of 2.20 eV. Which of these photosensitive surfaces may emit photoelectrons? [NEET 2023]$ (1) $Both Na and K$ (2) $K only$ (3) $Na only$ (4) $Cs only$ 59. $The work function of a photosensitive material is 4.0 eV The longest wavelength of light that can cause photon emission from the substance is (approximately)$ (1) $3100 nm$ (2) $966 nm$ (3) $31 nm$ (4) $310 nm$ 60. $A beam of cathode rays is subjected to crossed electric (E) and magnetic fields (B). The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by (Where V is the potential difference between cathode and anode)$ (1) $\frac{B ^{2}}{2 V E ^{2}}$ (2) $\frac{2 V B ^{2}}{E ^{2}}$ (3) $\frac{2 V E ^{2}}{B ^{2}}$ (4) $\frac{E ^{2}}{2 V B ^{2}}$