Dual Nature of Matter & Radiation PYQs Set 9 (PDF)

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Mere Teacher · Previous Year Questions NEET Physics · Dual Nature of Matter & Radiation · Set 9 (Q241-270)
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241. $An electron of mass m with an initial velocity v = v_{0} i (v_{0} > 0) enters an electric field E = - E i (E_{0} = constant > 0) at t = 0. If λ_{0} is its de‐Broglie wavelength initially, then its de‐Broglie wavelength at time t is$ (1) $\frac{λ _{0}}{( 1 + \frac{e E _{0}}{m v _{0}} t )}$ (2) $λ_{0} (1 + \frac{e E _{0}}{m v _{0}} t)$ (3) $λ_{0} t$ (4) $λ_{0} .$ 242. $The difference between threshold wavelengths for two metal surfaces A and B having work function φ_{A} = 9 eV and φ_{B} = 4. 5 eV in nm is: {Given, he = 1242 eV nm}$ (1) $540$ (2) $276$ (3) $264$ (4) $138$ 243. $Electrons of mass m with de‐Broglie wavelength λ fall on the target in an X ‐ray tube. The cutoff wavelength (λ_{0}) of the emitted X ‐ray is$ (1) $λ_{0} = \frac{2 mc λ ^{2}}{h}$ (2) $λ_{0} = \frac{2 h}{mc}$ (3) $λ_{0} = \frac{2 m ^{2} c ^{2} λ ^{3}}{h ^{2}}$ (4) $λ_{0} = λ$ 244. $As the intensity of incident light increases$ (1) $kinetic energy of emitted photoelectrons increases$ (2) $photoelectric current decreases$ (3) $photoelectric current increases$ (4) $kinetic energy of emitted photoelectrons decreases.$ 245. $Which of the following figure represents the variation of particle momentum and associated de Broglie wavelength?$ (1) (2) (3) (4) 246. $A source S_{1} is producing, 1 0^{15} photons per second of wavelength 5000 A^{\circ} . Another source S_{2} is producing 1.02 \times 1 0^{15} photons per second of wavelength 5100 A^{\circ} . Then, (power of S_{2}) / (power of S_{1}) is equal to$ (1) $1.00$ (2) $1.02$ (3) $1.04$ (4) $0.98$ 247. $The electric field of a plane electromagnetic wave is given by E = E_{0} (x^+ y^) sin (kz - ωt) Its magnetic field will be given by$ (1) $E0c(x^-y^)cos(kz-ωt)$ (2) $E0c(x^-y^)sin(kz-ωt)$ (3) $E0c(-x^+y^)sin(kz-ωt)$ (4) $E0c(x^+y^)sin(kz-ωt)$ 248. $A metal surface is illuminated by light of given intensity and frequency to cause photoemission. If the intensity of illumination is reduced to one fourth of its original value then maximum K.E. of the emitted photoelectrons would be$ (1) $twice the original value$ (2) $four times the original value$ (3) $one fourth of the original value$ (4) $unchanged.$ 249. $When a piece of metal is illuminated by a monochromatic light of wavelength λ, then stopping potential is 3 V_{s} . When same surface is illuminated by light of wavelength 2 λ, then stopping potential becomes V_{s} . The value of threshold wavelength for photoelectric emission will be$ (1) $4/3 λ$ (2) $6 λ$ (3) $4 λ$ (4) $8 λ$ 250. $In a photoelectric effect experiment a light of frequency 1.5 times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be:$ (1) $Doubled$ (2) $Quadrupled$ (3) $Zero$ (4) $Halved$ 251. $The additional energy that should be given to an electron to reduce its de-Broglie wavelength from 1 nm to 0.5 nm is$ (1) $four times initial energy$ (2) $thrice the initial energy$ (3) $equal to the initial energy$ (4) $twice the initial energy$ 252. $An α -particle, a proton and an electron have the same kinetic energy. Which one of the following is correct in case of their De-Broglie wavelength?$ (1) $λ_{α} > λ_{p} > λ_{e}$ (2) $λ_{α} < λ_{p} < λ_{e}$ (3) $λ_{α} = λ_{p} = λ_{e}$ (4) $λ_{α} > λ p < λ_{e}$ 253. $The ratio of the de-Broglie wavelengths for the electron and proton moving with the same velocity is (m_{p} -mass of proton, m_{e} -mass of electron)$ (1) $m_{p} : m_{e}$ (2) $m_{p}^{2} : m_{e}^{2}$ (3) $m_{e} : m_{p}$ (4) $m_{e}^{2} : m_{p}^{2}$ 254. $For a plane electromagnetic wave, the magnetic field at a point x and time t is B \to (x, t) = (1.2 \times 10^{- 7} sin (0.5 \times 10^{3} x + 1.5 \times 10^{11} t) k^) T The instantaneous electric field E \to corresponding to B \to is (speed of light c = 3 \times 10^{8} ms^{- 1})$ (1) $E \to (x, t) = (36 sin (1 \times 10^{3} x + 1.5 \times 10^{11} t) i^) \frac{v}{m}$ (2) $E \to (x, t) = (36 sin (0.5 \times 10^{3} x + 1.5 \times 10^{11} t) k^) \frac{V}{m}$ (3) $E \to (x, t) = (- 36 sin (0.5 \times 10^{3} x + 1.5 \times 10^{11} t) j^) \frac{V}{m}$ (4) $E \to (x, t) = (36 sin (1 \times 10^{3} x + 0.5 \times 10^{11} t) j^) \frac{v}{m}$ 255. $The electric field at the point associated with a light wave is given by E = 200 [sin(6 x 1 0^{15}) t + sin(9 x 1 0^{15}) t] V m^{- 1} Given: h = 4. 14 x 1 0^{- I 5} eVs If this light falls on a metal surface having a work function of 2.50 eV, the maximum kinetic energy of the photoelectrons will be:$ (1) $1.90 eV$ (2) $3.27eV$ (3) $3.60eV$ (4) $3.42 eV$ 256. $The work functions of Aluminium and Gold are 4.1 eV and 5.1 eV respectively. The ratio of the slope of the stopping potential versus frequency plot for Gold to that of Aluminium is$ (1) $1.24$ (2) $2$ (3) $1$ (4) $1.5$ 257. $Number of ejected photoelectrons increases with increase$ (1) $in intensity of light$ (2) $in wavelength of light$ (3) $in frequency of light$ (4) $never$ 258. $Which of the following statement is correct?$ (1) $The photocurrent increases with intensity of light$ (2) $The stopping potential increases with increase of incident light$ (3) $The current in photocell increases with increasing frequency$ (4) $The photocurrent is proportional to the applied voltage.$ 259. $A proton, an electron and an alpha particle have the same energies. Their de-Broglie wavelengths will be compared as:$ (1) $λ_{α} < λ_{p} < λ_{e}$ (2) $λ_{e} > λ_{α} > λ_{p}$ (3) $λ_{p} > λ_{e} > λ_{α}$ (4) $λ_{p} < λ_{e} < λ_{α}$ 260. $Maximum velocity of the photoelectron emitted by a metal is 1.8 \times 10^{6} m s^{- 1} . Take the value of specific charge of the electron is 1.8 \times 10^{11} C kg^{- 1} . Then the stopping potential in volt is$ (1) $1$ (2) $3$ (3) $9$ (4) $6$ 261. $Light of wavelength λ which is less than threshold wavelength is incident on a photosensitive material. If incident wavelength is decreased so that emitted photoelectrons are moving with some velocity then stopping potential will$ (1) $increase$ (2) $decrease$ (3) $be zero$ (4) $become exactly half.$ 262. $Ultraviolet radiations of 6.2 eV falls on an aluminium surface. Kinetic energy of fastest electron emitted is (work function = 4.2 eV)$ (1) $3.2 \times 1 0^{- 21} J$ (2) $3.2 \times 1 0^{- 19} J$ (3) $7 \times 1 0^{- 25} J$ (4) $9 \times 1 0^{- 32} J$ 263. $The graph between the maximum speed (v_{max}) of a photoelectron and frequency (v) of the incident radiation, in photoelectric effect is correctly represented by$ (1) (2) (3) (4) 264. $Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current, if the frequency is halved and intensity is doubled? [NEET 2020]$ (1) $Four times$ (2) $One-fourth$ (3) $Zero$ (4) $Doubled$ 265. $The variation of stopping potential (V_{0}) as a function of the frequency (v) of the incident light for a metal is shown in figure. The work function of the surface is$ (1) $2.98 eV$ (2) $2.07 eV$ (3) $1.36 eV$ (4) $18.6 eV$ 266. $According to Einstein's photoelectric equation, the graph between kinetic energy of photoelectrons ejected and the frequency of incident radiation is$ (1) (2) (3) (4) 267. $The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three different radiations. Which one of the following is a correct statement?$ (1) $Curves (a) and (b) represent incident radiations of same frequency but of different intensities.$ (2) $Curves (b) and (c) represent incident radiations of different frequencies and different intensities.$ (3) $Curves (b) and (c) represent incident radiations of same frequency having same intensity.$ (4) $Curves (a) and (b) represent incident radiations of different frequencies and different intensities$ 268. $Following graphs show the variation of stopping potential corresponding to the frequency of incident radiation (u) for a given metal. The correct variation is shown in graph (v_{0} =) Threshold frequency)$ (1) (2) (3) (4) 269. $From the following graph of photocurrent against collector plate potential, for two different intensities of light I_{1} and I_{2}, one can conclude$ (1) $I_{1} = I_{2}$ (2) $I_{1} > I_{2}$ (3) $I_{1} < I_{2}$ (4) $Comparison is not possible$ 270. $A small mirror of mass m is suspended by a massless thread of length l . Then the small angle through which the thread will be deflected when a short pulse of laser of energy E falls normal on the mirror (c = speed of light in vacuum and g = acceleration due to gravity)$ (1) $θ = \frac{E}{mc gl}$ (2) $θ = \frac{E}{2 mc gl}$ (3) $θ = \frac{3 E}{4 mc gl}$ (4) $θ = \frac{2 E}{mc gl}$