Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

61.

The angle of incidence at which reflected light totally polarized for reflection from air to glass (refractive index n), is

  • sin−1 (n

  • sin−1 (1/n)

  • tan−1 (1/n)

  • tan−1 (1/n)

286 Views

62.

The maximum number of possible interference maxima for slit-separation equal to twice the wavelength in Young’s double-slit experiment is

  • infinite

  • five

  • three

  • three

270 Views

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63.

An electromagnetic wave of frequency ν = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ε = 4.0. Then

  • wavelength is doubled and the frequency remains unchanged

  • wavelength is doubled and frequency becomes half

  • wavelength is halved and frequency remains unchanged

  • wavelength is halved and frequency remains unchanged


C.

wavelength is halved and frequency remains unchanged

In vacuum, ε0 = 1
In medium, ε = 4
So, refractive index



Hence, it is clear that wavelength and velocity will become half but frequency remains unchanged when the wave is passing through any medium.

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64.

Two spherical conductor B and C having equal radii and carrying equal charges in them repel each other with a force F when kept apart at some distance. A third spherical conductor having same radius as that of B but uncharged brought in contact with B, then brought in contact with C and finally removed away from both. The new force of repulsion, between B and C is

  • F/4

  • 3F/4

  • 3F/8

  • 3F/8

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65.

The thermistors are usually made of

  • metals with low temperature coefficient of resistivity

  • metals with high temperature coefficient of resistivity

  • metal oxides with high temperature coefficient of resistivity ‘

  • metal oxides with high temperature coefficient of resistivity ‘

206 Views

66.

According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal Vs the frequency, of the incident radiation gives 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

  • depends both on the intensity of the radiation and the metal used

193 Views

67.

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

  • 540 nm

  • 400 nm

  • 310 nm,

  • 310 nm,

350 Views

68.

A nucleus disintegrates into two nuclear parts which have their velocities in the ratio 2:1. The ratio of their nuclear sizes will be

  • 21/3:1

  • 1:31/2

  • 31/2:1

  • 31/2:1

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69.

The binding energy per nucleon of deuteron (21H) and helium nucleus (42He) is 1.1 MeV and 7 MeV respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is

  • 13.9 MeV

  • 26.9 MeV

  • 23.6 MeV

  • 23.6 MeV

551 Views

70.

An α-particle of energy 5 MeV is scattered through 180° by a fixed uranium nucleus. The distance of the closest approach is of the order of

  • 1 Å

  • 10−10 cm

  • 10−12 cm

  • 10−12 cm

1123 Views

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