Physics
Stars twinkle because

the distance of the stars from the earth changes with time.
the intensity of light emitted by them changes with time.
the refractive index of the different layers of the earth's atmosphere ch
None of these

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Physics
Which one of the following is not a property of electromagnetic waves?

Electromagnetic waves do not require a medium to propagate.
Oscillating electric field and magnetic field are perpendicular to each other.
Electromagnetic waves are transverse waves
Electromagnetic waves do not show interference and diffraction.

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