If  λν,  λx and  &

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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


C.

λm> λv > λx

Wavelength order of given rays are listed below:
Rays Wavelength (Ao)
Visible light 4000 - 7000
X - rays 1 - 100
Microwaves 107 - 109

Obviously, λx< λν< λm 

or λ m> λ v > λ x

Visible light, X-rays and microwaves are all electromagnetic waves.


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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


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.


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