Dual Nature of Matter & Radiation PYQs Set 7 (PDF)

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Set 7 of 11 · Questions 181-210 of 321

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Mere Teacher · Previous Year Questions JEE Main Physics · Dual Nature of Matter & Radiation · Set 7 (Q181-210)
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181. $An electron is accelerated through a potential difference of 10000 V. Its de-Broglie wavelength is nearly (m_{e} = 9 \times 10^{- 31} kg) [NEET 2019]$ (1) $12.2 \times 10^{- 12} m$ (2) $12.2 \times 10^{- 14} m$ (3) $12.2 nm$ (4) $12.2 \times 10^{- 13} m$ 182. $When a certain metal surface is illuminated with light of frequency v, the stopping potential for photoelectric current is V_{0} . When the same surface is illuminated by light of frequency \frac{V}{2}, the stopping potential is \frac{V _{0}}{4}, the threshold frequency for photoelectric emission is$ (1) $\frac{v}{6}$ (2) $\frac{v}{3}$ (3) $\frac{2 v}{3}$ (4) $\frac{40}{3}$ 183. $The de Broglie wavelength of a charged particle accelerated through a potential difference V is λ . If the potential difference is increased by 21 %, the de Broglie wavelength of the charged particle is$ (1) $\frac{5 λ}{9}$ (2) $\frac{7 λ}{9}$ (3) $\frac{9 λ}{11}$ (4) $\frac{10 λ}{11}$ 184. $A photo emissive substance is illuminated with a radiation of wavelength λ_{i} so that it releases electrons with de-Broglie wavelength λ_{e} . The longest wavelength of radiation that can emit photoelectron is λ_{o} . Expression for de-Broglie wavelength is given by: (m: mass of the electron, h: Planck's constant and c: speed of light)$ (1) $λ_{e} = \frac{h λ _{i}}{2 mc}$ (2) $λ_{e} = \frac{h}{2 mc ( \frac{1}{λ _{i}} - \frac{1}{λ _{o}} )}$ (3) $λ_{e} = \frac{h}{2 mc ( \frac{1}{λ _{i}} - \frac{1}{λ _{o}} )}$ (4) $λ_{e} = \frac{h λ _{0}}{2 mc}$ 185. $The de Broglie wavelength ' λ' of a particle$ (1) $is proportional to mass$ (2) $is proportional to impulse$ (3) $is inversely proportional to impulse$ (4) $does not depend on impulse$ 186. $When photons of energy hv fall on metal plate of work function ' W_{0}', photoelectrons of maximum kinetic energy ' K' are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will appear$ (1) $K + W_{0}$ (2) $K + hv$ (3) $K^{’}$ (4) $2 K^{’}$ 187. $Photons with energy 5 eV are incident on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectrons will reach the anode A, if the stopping potential of A relative to C is [NEET 2016]$ (1) $+3 V$ (2) $+4 V$ (3) $-1 V$ (4) $-3 V$ 188. $An isolated lead ball is charged upon continuous irradiation by EM, radiation of wavelength, λ = 221 nm . The maximum potential attained by the lead ball, if its work function is 4.14 eV is (take, h = 6.63 \times 10^{- 34} J - s, c = 3 \times 10^{8} m / s, e = 1.6 \times 10^{- 19} C)$ (1) $1.49 V$ (2) $2.67 V$ (3) $3.14 V$ (4) $0.51 V$ 189. $A source of light is placed at a distance of 50 cm from a photo cell and the stopping potential is found to be V_{0} . If the distance between the light source and photo cell is made 25 cm, the new stopping potential will be:$ (1) $V_{0} /2$ (2) $V_{0}$ (3) $4 V_{0}$ (4) $2 V_{0}$ 190. $The energy of an electron having de-Broglie wavelength ' λ' is (h = Planck's constant, m = mass of electron)$ (1) $\frac{h}{2 mλ}$ (2) $\frac{h ^{2}}{2 m λ ^{2}}$ (3) $\frac{h ^{2}}{2 m ^{2} λ ^{2}}$ (4) $\frac{h ^{2}}{2 m ^{2} λ}$ 191. $A plane electromagnetic wave, has frequency of 2.0 \times 10^{10} Hz and its energy density is 1.02 \times 10^{- 8} J / m^{3} in vacuum. The amplitude of the magnetic field of the wave is close to (\frac{1}{4 π ϵ _{0}} = 9 \times 10^{9} \frac{Nm ^{2}}{C ^{2}}) and speed of light = 3 \times 10^{8} ms^{- 1})$ (1) $190 nT$ (2) $160 nT$ (3) $150 nT$ (4) $180 nT$ 192. $The threshold frequency of metal is f_{0} . When the light of frequency 2 f_{0} is incident on the metal plate, the maximum velocity of photoelectron is v_{1} . When the frequency of incident radiation is increased to 5 f_{0} . the maximum velocity of photoelectrons emitted is v_{2} . The ratio of v_{1} to v_{2} is:$ (1) $\frac{v _{1}}{v _{2}} = \frac{1}{2}$ (2) $\frac{v _{1}}{v _{2}} = \frac{1}{8}$ (3) $\frac{v _{1}}{v _{2}} = \frac{1}{16}$ (4) $\frac{v _{1}}{v _{2}} = \frac{1}{4}$ 193. $Which of the following is not the property of cathode rays?$ (1) $It produces heating effect$ (2) $It does not deflect in electric field$ (3) $It casts shadow$ (4) $It produces fluorescence.$ 194. $J.J. Thomson’s cathode‐ray tube experiment demonstrated that$ (1) $cathode rays are streams of negatively charged ions$ (2) $all the mass of an atom is essentially in the nucleus$ (3) $the e / m of electrons is much greater than the e / m of protons$ (4) $the ratio of the cathode‐ray particles changes when a different gas is placed in the discharge tube$ 195. $The de Broglie wavelength of an electron having kinetic energy E is λ . If the kinetic energy of electron becomes \frac{E}{4}, then its de-Broglie wavelength will be:$ (1) $2 λ$ (2) $\frac{λ}{2}$ (3) $\frac{λ}{2}$ (4) $2 λ$ 196. $In a plane electromagnetic wave, the directions of electric field and magnetic field are represented by k^and 2 i^- 2 j^respectively. What is the unit vector along direction of propagation of the wave?$ (1) $\frac{1}{5} (i^+ 2 j^)$ (2) $\frac{1}{2} (j^+ k^)$ (3) $\frac{1}{2} (i^+ j^)$ (4) $\frac{1}{5} (2 i^+ j^)$ 197. $If ultraviolet radiation of 6.2 eV falls of an aluminium surface, then kinetic energy of the fastest emitted electron is (work-function = 4.2 eV)$ (1) $3.2 \times 10^{- 19} J$ (2) $3.2 \times 10^{- 21} J$ (3) $7 \times 10^{- 25} J$ (4) $9 \times 10^{- 31} J$ 198. $The kinetic energy of emitted electron is E when the light incident on the metal has wavelength λ . To double the kinetic energy, the incident light must have wavelength:$ (1) $\frac{hc}{Eλ - hc}$ (2) $\frac{hcλ}{Eλ + hc}$ (3) $\frac{hλ}{Eλ + hc}$ (4) $\frac{hcλ}{Eλ - hc}$ 199. $A proton and an α particle are accelerated through the same potential difference V . The ratio of their de Broglie wavelengths is$ (1) $2$ (2) $22$ (3) $3$ (4) $23$ 200. $A proton and an α-particle are accelerated from rest to the same energy. The de-Broglie wavelengths λ_{p} and λ_{α} are in the ratio [NEET 2019]$ (1) $2 : 1$ (2) $1 : 1$ (3) $2 : 1$ (4) $4 : 1$ 201. $If an electron has an energy such that its de-Broglie wavelength is 5500Å, then the energy value of that electron is (h = 6.6 \times 10^{- 34} Js, m_{e} = 9.1 \times 10^{- 31} kg)$ (1) $8 \times 10^{- 20} J$ (2) $8 \times 10^{- 10} J$ (3) $8 J$ (4) $8 \times 10^{- 25} J$ 202. $The kinetic energy of the photoelectrons increases by 0.52 eV when the wavelength of incident light is changed from 500 nm to another wavelength which is approximately$ (1) $1250 nm$ (2) $700 nm$ (3) $1000 nm$ (4) $400 nm$ 203. $In a photoelectric effect experiment the cathode metal is exposed to light of wavelength 600 nm . The maximum kinetic energy of the ejected electron doubles when light of wavelength 400 nm is used. The work function of the cathode metal is approximately. [Use h = 6.63 \times 10^{- 34} J - s, c = 3 \times 10^{8} m / s]$ (1) $1.58 eV$ (2) $1.84 eV$ (3) $1.02 eV$ (4) $2.64 eV$ 204. $The work function of a surface of a photosensitive material is 6.2 eV The wavelength of the incident radiation for which the stopping potential is 5 V lies in the$ (1) $Infrared region$ (2) $X ‐ray region$ (3) $Ultraviolet region$ (4) $Visible region$ 205. $The work function of a metal is 1 eV . Light of wavelength 3000Å is incident on this metal surface. The velocity of emitted photoelectrons will be$ (1) $10 m s^{- 1}$ (2) $1 \times 10^{3} m s^{- 1}$ (3) $1 \times 10^{4} m s^{- 1}$ (4) $1 \times 10^{6} m s^{- 1}$ 206. $Average force exerted on a non-reflecting surface at normal incidence is 2.4 \times 10^{- 4} N . If 360 W / cm^{2} is the light energy flux during span of 1 hour 30 minutes, Then the area of the surface is:$ (1) $0.2 m^{2}$ (2) $20 m^{2}$ (3) $0.1 m^{2}$ (4) $0.02 m^{2}$ 207. $What is the maximum wavelength of electromagnetic radiation that create a electron-hole pair in material with band gap 0.7 eV ? Planck's constant = 4.136 \times 1 0^{- 15} eV-s, velocity of light = 3 \times 1 0^{8} m/s.$ (1) $1773 \times 10^{- 8} m$ (2) $1773 \times 10^{- 9} m$ (3) $1873 \times 10^{- 9} m$ (4) $1873 \times 10^{- 8} m$ 208. $For photoelectric effect which of the following statements are true. (I) The kinetic energies of the photoelectrons do not depend on the frequency of light (II) Photoelectric effect will always occur for highly intense light (III)The maximum kinetic energy of photoelectron does not depend upon the intensity of the light (IV)The escaping electron's kinetic energy is larger for larger frequency$ (1) $I and II only$ (2) $II and III only$ (3) $III and IV only$ (4) $IV and I only$ 209. $An electron in the ground state of the hydrogen atom has the orbital radius of 5.3 10^{- 11} m while that for the electron in third excited state is 8.48 \times 10^{- 10} m . The ratio of the de Broglie wavelengths of electron in the excited state to that in the ground state is$ (1) $3$ (2) $16$ (3) $9$ (4) $4$ 210. $When light of frequency twice the threshold frequency is incident on the metal plate, the maximum velocity of emitted election is v_{1} . When the frequency of incident radiation is increased to five times the threshold value, the maximum velocity of emitted electron becomes v_{2} . If v_{2} = x v_{1}, the value of x will be______.$