Assertion:  In electromagnetic waves electric field and

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 Multiple Choice QuestionsMultiple Choice Questions

51.

If  λν,  λx and  λmrepresent the wavelengths of visible light, X-rays and microwaves respectively, then

  • λ m > λ x >  λ ν

  • λv >λm > λx

  • λm> λv > λx

  • λv >  λx >  λm


52.

In gamma ray emission from a nucleus

  • both the neutron number and the proton number change

  • there is no change in the proton number and the neutron number

  • only the neutron number changes

  • only the proton number changes


53.

Which of the following electromagnetic waves have the  smallest wavelength?

  • γ - rays

  • X- rays

  • UV waves

  • infrared rays


54.

X-rays are used in determining the molecular structure of crystalline because

  • its energy is high

  • it can penetrate the material

  • its wavelength is comparable to interatomic distance

  • its frequency is low


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55.

Assertion:  The electromagnetic waves are transverse in nature.

Reason:  Waves of wavelength 10 µm are radiowave and microwave.

  • 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.


56.

Assertion:  UV radiation causes photodissociation of ozone into O2 and O, thus causing damage to the stratospheric ozone layer. 

Reason:  Ozone hole is resulting in global warming and climate change.

  • 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


57.

Assertion:  Electromagnetic waves with frequencies smaller than the critical frequencies of ionosphere cannot be used for communication using sky wave propagation. 

Reason: The refractive index of the ionosphere becomes very high for frequencies higher than the critical frequency.

  • 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.


58.

Assertion: Electromagnetic radiations exert pressure. 

Reason:  Electromagnetic-waves carry both momentum and energy.

  • 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.


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59.

The frequency order for X-rays ( A), γ-rays (B), UV rays (C) is

  • B > A > C

  • A > B  > C

  • C > B > A

  • A > C > B


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60.

Assertion:  In electromagnetic waves electric field and magnetic field lines are perpendicular to each other.
Reason: Electric field and magnetic field are self sustaining.

  • 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.


B.

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

Electromagnetic waves are those waves in which there are sinusoidal variation of electric and magnetic field vectors at right angles to each other as well as at right angles to the direction of wave propagation. They are self-sustaining oscillations of electric and magnetic fields in free space or vacuum.


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