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# NEET Physics  Dual Nature of Radiation & Matter  Practice Q & A

1. Find the de–Broglie wavelength of an electron with kinetic energy of 120 eV.

 112 pm 95 pm 124 pm 102 pm

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2. 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 2 λ, the stopping potential is 4/V. The threshold wavelength for the metallic surface is

 5/2 λ 3 λ 4 λ 5 λ

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3. The de Broglie wavelength of an electron accelerated to a potential of 400 V is approximately

 0.03 nm 0.04 nm 0.12 nm 0.06 nm

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4. A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 1/2 m away , the number of electrons emitted by photocathode would

 increase by a factor of 4 decrease by a factor of 4 increase by a factor of 2 decrease by a factor of 2

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5. Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively, successively illuminate a metallic surface whose work function is 0.5 eV. Ratio of maximum speeds of emitted electrons will be

 1 : 2 1 : 5 1 : 1 1 : 4

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6. An α–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

 10 Å 0.01 Å 1 Å 0.1 Å

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7. Statement–1 : When ultraviolet light is incident on a photocell, its stopping potential is V0 and the maximum kinetic energy of the photoelectrons is Kmax. When the ultraviolet light is replaced by X–rays, both V0 and Kmax increase.
Statement–2 : Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.

 Statement–1 is true, Statement–2 is false Statement–1 is false, Statement–2 is true Statement–1 is true, Statement–2 is true; Statement–2 is the correct explanation of Statement–1 Statement–1 is true, Statement–2 is true; Statement–2 is the not the correct explanation of Statement–1

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8. The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately:

 540 nm 400 nm 310 nm 220 nm

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9. According to Einstein s photoelectric equation, the plot of the kinetic energy of the emitted photoelectrons from a metal Vs the frequency, of the incident radiation gives a straight line whose slope:

 depends on the nature of the metal used depends on the intensity of the radiation depends both on the intensity of the radiation and the metal used is the same for all metals and independent of the intensity of the radiation

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10. 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

 +3 V +4 V –1 V –3 V

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