Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

Proton, Deuteron and alpha particle of the same kinetic energy is moving in circular trajectories in a constant magnetic field. The radii of the proton, deuteron and alpha particle are respectively rp, rd and rα. Which one of the following relations is correct?

  •  rα = rp= rd

  •  rα = rp< rd

  •  rα > rd> rp

  •  rα > rd> rp

808 Views

22.

An object 2.4 m in front of a lens forms a sharp image on a film 12 cm behind the lens. A glass plate 1cm thick, of refractive index 1.50 is interposed between lens and film with its plane faces parallel to film. At what distance (from lens) should object be shifted to be in sharp focus on film? 

  • 7.2 m

  • 2.4 m

  • 3.2 m

  • 3.2 m

522 Views

23.

A cylindrical tube, open at both ends, has a fundamental frequency, f, in the air. The tube is dipped vertically in water so that half of it is in water. The fundamental frequency of the air-column is now

  • f

  • f/2

  • 3f/4

  • 3f/4

313 Views

24.

Assume that a neutron breaks into a proton and an electron. The energy released during this process is(Mass of neutron = 1.6725 x 10–27kg; mass of proton = 1.6725 x 10–27kg; mass of electron = 9 x 10–31kg)

  • 0.73 MeV

  • 7.10 MeV

  • 6.30 MeV

  • 6.30 MeV

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25.

A radar has a power of 1 Kw and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth = 6.4 x 106 m) is

  • 80 km

  • 16 km

  • 40km

  • 40km

321 Views

26.

Truth table for system of four NAND gates as shown in figure is

280 Views

27.

A charge Q is uniformly distributed over the surface of non conducting disc of radius R. The disc rotates about an axis perpendicular to its plane and passing through its centre with an angular velocity ω. As a result of this rotation, a magnetic field of induction B is obtained at the centre of the disc. If we keep both the amount of charge placed on the disc and its angular velocity to be constant and vary the radius of the disc than the variation of the magnetic induction at the centre of the disc will be represented by the figure

817 Views

28.

This question has statement 1 and statement 2. Of the four choices given after the statements, choose the one that best describes the two statements
Statement 1: Davisson – Germer experiment established the wave nature of electrons.
Statement 2: If electrons have wave nature, they can interfere and show diffraction.

  • Statement 1 is false, Statement 2 is true

  • Statement 1 is true, Statement 2 is false

  • Statement 1 is true, Statement 2 is the correct explanation for statement 1

  • Statement 1 is true, Statement 2 is the correct explanation for statement 1

155 Views

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29.

In Young's double slit experiment, one of the slit is wider than other, so that the amplitude of the light from one slit is double of that from other slits. If Im be the maximum intensity, the resultant intensity I when they interfere at phase difference φ is given by

  • straight I subscript straight m over 9 left parenthesis 4 space plus 5 space cos space straight ϕ right parenthesis
  • straight I subscript straight m over 3 open parentheses 1 space plus space 2 space cos squared space straight ϕ over 2 close parentheses
  • straight I subscript straight m over 5 open parentheses 1 space plus 4 space cos squared straight ϕ over 2 close parentheses
  • straight I subscript straight m over 5 open parentheses 1 space plus 4 space cos squared straight ϕ over 2 close parentheses


D.

straight I subscript straight m over 5 open parentheses 1 space plus 4 space cos squared straight ϕ over 2 close parentheses

Let A1 = A0, A2 = 2A0
If amplitude of resultant wave is A then

straight A squared space equals space straight A subscript 1 superscript 2 space plus space straight A subscript 2 superscript 2 space plus 2 straight A subscript 1 straight A subscript 2 space cos space straight ϕ
 For maximum intensity

straight A subscript max superscript 2 space equals space straight A subscript 1 superscript 2 space plus space straight A subscript 2 superscript 2 space plus 2 straight A subscript 1 straight A subscript 2
therefore fraction numerator straight A squared over denominator straight A subscript max superscript 2 end fraction space equals space fraction numerator straight A subscript 1 superscript 2 space plus straight A subscript 2 superscript 2 space plus 2 straight A subscript 1 straight A subscript 2 space cos space straight ϕ over denominator straight A subscript 1 superscript 2 space plus straight A subscript 2 superscript 2 space plus space 2 straight A subscript 1 straight A subscript 2 end fraction
space equals space fraction numerator straight A subscript 0 superscript 2 space plus space 4 straight A subscript 0 superscript 2 space plus space 2 left parenthesis straight A subscript 0 right parenthesis left parenthesis 2 straight A subscript 0 right parenthesis cos space straight ϕ over denominator straight A subscript 0 superscript 2 space plus space 4 straight A subscript 0 superscript 2 space plus space 2 left parenthesis straight A subscript 0 right parenthesis left parenthesis 2 straight A subscript straight o right parenthesis end fraction
straight I over straight I subscript straight m space equals space fraction numerator 5 space plus 4 space cos space straight ϕ over denominator 9 end fraction space equals space fraction numerator 1 space plus space 8 space cos squared space left parenthesis straight ϕ divided by 2 right parenthesis over denominator 9 end fraction

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30.

The hydrogen atom is excited from ground state to another state with the principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be

  • 2

  • 3

  • 3

  • 3

218 Views

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