Dual Nature of Matter & Radiation PYQs Set 4 (PDF)

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Mere Teacher · Previous Year Questions NEET Physics · Dual Nature of Matter & Radiation · Set 4 (Q91-120)
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91. $A particle of charge q, mass m and energy E has deBroglie wavelength λ . For a particle of charge 2 q, mass 2 m and energy 2 E, the de-Broglie wavelength is$ (1) $\frac{λ}{4}$ (2) $2 λ$ (3) $8 λ$ (4) $\frac{λ}{2}$ 92. $Monochromatic light of frequency 6. \times 1 0^{14} Hz is produced by a laser. The power emitted is 2 \times 1 0^{- 3} W The number of photons emitted, on the average, by the source per second is$ (1) $5 \times 1 0^{16}$ (2) $5 \times 1 0^{17}$ (3) $5 \times 1 0^{14}$ (4) $5 \times 1 0^{15}$ 93. $The work function of a metal is 3 eV. The color of the visible light that is required to cause emission of photoelectrons is$ (1) $Red$ (2) $Green$ (3) $Blue$ (4) $Yellow$ 94. $An (x‐particle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of 0.25 Wb / m^{2} . The de Broglie wavelength associated with the particle will be$ (1) $1 A ˚$ (2) $0.1 A ˚$ (3) $10 A ˚$ (4) $0.01 A ˚$ 95. $The de-Broglie wavelength of an electron with kinetic energy of 320 eV is (Take h = 6.0 \times 10^{- 34} SI unit, mass of electron = m_{e} = 9.0 \times 10^{- 31} kg . Charge of an electron = 1.6 \times 10^{- 19} C)$ (1) $85.8 pm$ (2) $110.5 pm$ (3) $62.5 pm$ (4) $50 pm$ 96. $The electric field of a plane electromagnetic wave propagating along the x direction in vacuum is E = E_{0} j^cos (ωt - kx) . The magnetic field B \to at the moment t = 0 is$ (1) $B = E_{0} μ_{0} ϵ_{0} cos (kx) j^$ (2) $B = E_{0} μ_{0} ϵ_{0} cos (kx) k^$ (3) $B = \frac{E _{0}}{μ _{0} ϵ _{0}} cos (kx) k^$ (4) $B = \frac{E _{0}}{μ _{0} ϵ _{0}} cos (kx) j^$ 97. $The work functions for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV According to Einstein’s equation the metals which will emit photoelectrons for a radiation of wavelength 4100 Å is/are$ (1) $A only$ (2) $A and B only$ (3) $all the three metals$ (4) $none.$ 98. $When radiation of wavelength ' λ' is incident on a metallic surface, the stopping potential is 4.8 V . If the surface is illuminated with radiation of double the wavelength then the stopping potential becomes 1.6 V. The threshold wavelength for the surface is$ (1) $2 λ$ (2) $4 λ$ (3) $6 λ$ (4) $8 λ$ 99. $Photoelectric emission occurs only when the incident light has more than a certain minimum$ (1) $power$ (2) $wavelength$ (3) $intensity$ (4) $frequency$ 100. $A 5 watt source emits monochromatic light of wavelength 5000Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of$ (1) $8$ (2) $16$ (3) $2$ (4) $4$ 101. $An electron is moving with an initial velocity v = v_{0} i and is in a uniform magnetic field B = B_{0} j . Then its de Broglie wavelength$ (1) $decreases with time$ (2) $remains constant$ (3) $increase and decreases periodically$ (4) $increases with time.$ 102. $The threshold frequency of a metal with work function 6.63 eV is:$ (1) $16 \times 10^{15} Hz$ (2) $16 \times 10^{12} Hz$ (3) $1.6 \times 10^{12} Hz$ (4) $1.6 \times 10^{15} Hz$ 103. $When a metallic surface is illuminated with radiation of wavelength λ, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is V /4 . The threshold wavelength for the metallic surface is [NEET 2016]$ (1) $5λ$ (2) $\frac{5}{2} λ$ (3) $3λ$ (4) $4λ$ 104. $Two streams of photons, possessing energies to five and ten times the work function of metal are incident on the metal surface successively. The ratio of the maximum velocities of the photoelectron emitted, in the two cases respectively, will be$ (1) $1 : 2$ (2) $1 : 3$ (3) $2 : 3$ (4) $3 : 2$ 105. $The de Broglie wavelength of a molecule in a gas at room temperature (300 K) is λ_{1} . If the temperature of the gas is increased to 600 K, then the de Broglie wavelength of the same gas molecule becomes$ (1) $\frac{1}{2} λ_{1}$ (2) $2 λ_{1}$ (3) $\frac{1}{2} λ_{1}$ (4) $2 λ_{1}$ 106. $The energy E and momentum p of a moving body of mass m are related by some equation. Given that c represents the speed of light, identify the correct equation$ (1) $E^{2} = pc^{2} + m^{2} c^{2}$ (2) $E^{2} = p^{2} c^{2} + m^{2} c^{2}$ (3) $E^{2} = pc^{2} + m^{2} c^{4}$ (4) $E^{2} = p^{2} c^{2} + m^{2} c^{4}$ 107. $When two monochromatic lights of frequency v and v/2 are incident on a photoelectric metal, their stopping potential becomes V_{s} /2 and V_{s}, respectively. The threshold frequency for this metal is [NEET 2022]$ (1) $3v$ (2) $\frac{2}{3} v$ (3) $\frac{3}{2} v$ (4) $2v$ 108. $A proton moving with one tenth of velocity of light has a certain de Broglic wavelength of λ . An alpha particle having certain kinetic energy has the same de-Brogle wavelength λ . The ratio of kinetic energy of proton and that of alpha particle is:$ (1) $2 : 1$ (2) $4 : 1$ (3) $1 : 2$ (4) $1 : 4$ 109. $The retarding potential necessary to stop the emission of photoelectrons, when a target material of work function 1.24 eV is irradiated with light of wavelength 4.36 \times 10^{- 7} m is$ (1) $4.08 eV$ (2) $2.84 eV$ (3) $1.60 eV$ (4) $0.36 eV$ 110. $Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW The number of photons arriving per sec. on the average at a target irradiated by this beam is$ (1) $3 \times 1 0^{16}$ (2) $9 \times 1 0^{15}$ (3) $3 \times 1 0^{19}$ (4) $9 \times 1 0^{17}$ 111. $An electron of mass ' m' with an initial velocity v = v_{0} i (v_{0} > 0) enters an electric field E - E_{0} k . If the initial de Broglie wavelength is λ_{0}, the value after time t would be$ (1) $\frac{λ _{0}}{1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}}$ (2) $λ_{o} 1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{o}^{2}}$ (3) $λ_{0} 1-e2E0t2t2m2v02$ (4) $λ_{0}$ 112. $Radiation of wavelength 300 nm and intensity 100 W - m^{- 2} falls on the surface of a photosensitive material. If 2 % of the incident photons produced photoelectron, the number of photoelectrons emitted from an area of 2 cm^{2} of the surface is nearly$ (1) $15 \times 10^{11}$ (2) $6.04 \times 10^{14}$ (3) $1.5 \times 10^{12}$ (4) $60.4 \times 10^{15}$ 113. $A particle of mass 2 \times 10^{- 27} kg has de-Broglie wavelength of 3.3 \times 10^{- 10} m . The kinetic energy of this particle is. (Plank's Constant h h = 6.6 \times 10^{- 34} J - s)$ (1) $5 \times 10^{- 20} J$ (2) $8 \times 10^{- 20} J$ (3) $1 \times 10^{- 21} J$ (4) $6 \times 10^{- 22} J$ 114. $When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV The work function of the metal is$ (1) $0.65 eV$ (2) $1.0 eV$ (3) $1.3 eV$ (4) $1.5 eV$ 115. $A proton and an a-particle are accelerated from rest by 2 V and 4 V potentials, respectively. The ratio of their de-Broglie wavelength is:$ (1) $8 : 1$ (2) $2 : 1$ (3) $4 : 1$ (4) $16 : 1$ 116. $A beam of white light is incident normally on a plane surface absorbing 70 % of the light and reflecting the rest. If the incident beam carries 10 W of power, the force exerted by it on the surface is$ (1) $3.3 \times 10^{- 8} N$ (2) $4.33 \times 10^{- 8} N$ (3) $2.3 \times 10^{- 8} N$ (4) $3.53 \times 10^{- 8} N$ 117. $In an experiment with photoelectric effect, the stopping potential,$ (1) $increases with increase in the intensity of the incident light$ (2) $decreases with increase in the intensity of the incident light$ (3) $increases with increase in the wavelength of the incident light$ (4) $is (\frac{1}{e}) times the maximum kinetic energy of the emitted photoelectrons$ 118. $A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then$ (1) $each emitted electron carries one quarter of the initial energy$ (2) $number of electrons emitted is half the initial number$ (3) $each emitted electron carries half the initial energy$ (4) $number of electrons emitted is a quarter of the initial number.$ 119. $An electromagnetic wave of wavelength λ is incident on a photosensitive surface of negligible work function. If m mass of photoelectron emitted from the surface has de-Broglie wavelength λ_{d}, then [NEET 2021]$ (1) $λ = (\frac{2 h}{mc}) λ_{d}^{2}$ (2) $λ = (\frac{2 m}{hc}) λ_{d}^{2}$ (3) $λ = (\frac{2 mc}{h}) λ^{2}$ (4) $λ = (\frac{2 mc}{h}) λ_{d}^{2}$ 120. $An electron of mass m_{e} and a proton of mass m_{p} are moving with the same speed. The ratio of their de-Broglie's wavelengths \frac{λ _{e}}{λ _{p}} is$ (1) $1$ (2) $1836$ (3) $\frac{1}{1836}$ (4) $918$