The dimensional formula of Planck's constant is from Physics Dua

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 Multiple Choice QuestionsMultiple Choice Questions

151.

de Broglie wavelength λ associated with neutrons is related with absolute temperature T as

  • λ ∝ T

  • λ ∝ 1T

  • λ ∝ 1T

  • λ ∝  T2


152.

Light with an energy flux of 18 W/cm2 falls on a non-reflecting surface at normal incidence. The pressure exerted on the surface is

  • 2 N/m2

  • 2 × 10-4 N/m2

  • 6 N/m2

  • 6 × 10-4 N/m2


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153.

The dimensional formula of Planck's constant is

  • [ M L2 T-1 ]

  • [ M L2 T-2 ]

  • [ M L0 T2 ]

  • [ M L T2 ]


A.

[ M L2 T-1 ]

Planck's constant = Energy ( E ) / frequency ( ν )

Energy = [ M L2 T-2 ]

Frequency = [ M0 L0 T-1 ]

Planck's constant = M L2 T -2T -1

Planck's constant h = [M L2 T-1 ]


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154.

If  the  kinetic  energy  of  a  particle  is  increased  by  16  times,  the  percentage  change  in  the  de Broglie  wavelength  of  the particle  is

  • 25 %

  • 75 %

  • 60 %

  • 50 %


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155.

Assertion:  A photon has no rest mass, yet it carries definite momentum.

Reason:  Momemtum of photon is due to its energy and hence its equivalent mass.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


156.

Which of the following is matched wrongly?

  • Oil drop experiment  → Millikan

  • Dual nature of light → de Broglie

  • Uncertainty principle → Heisenberg

  • None of these


157.

Assertion: Stopping potential depends upon the frequency of incident light but is independent of the intensity of the light. 

Reason:  The maximum kinetic energy of the photoelectrons is proportional to stopping potential.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false.


158.

Hard X - rays for the study of fractures in bones should have a minimum wavelength of 10-11 m. The accelerating voltage for electrons in X-ray machine should be

  • < 124.2 kV

  • > 124.2 kV

  • between 60 kV and 70 kV

  • = 100 kV


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159.

In photoelectric effect, the electrons are ejected from metals if the incident light has a certain minimum

  • wavelength

  • frequency

  • amplitude

  • angle of incidence


160.

Flash light equipped with a new set of batteries, produces bright white light. As the batteries wear out

  • the light intensity gets reduced with no change in its colour

  • light colour changes first to yellow and then red with no change in intensity

  • it stops working suddenly while giving white light

  • colour changes to red and also intensity gets reduced


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