Stars twinkle because A. the intensity of light emitted by them changes with time. B. the distance of the stars from the earth changes with time. C. the refractive index of the different layers of the earth’s atmosphere changes continuously. D. None of these

The correct answer is C. The refractive index of the different layers of the earth’s atmosphere changes continuously.

When light travels from one medium to another, it bends. This is called refraction. The amount of refraction depends on the difference in the refractive indices of the two media. The refractive index of air is not constant, but changes with temperature, pressure, and humidity. These changes in the refractive index of air cause the light from stars to bend as it travels through the atmosphere. This bending causes the stars to appear to twinkle.

The intensity of light emitted by stars does not change with time. The distance of stars from the Earth does change with time, but this change is very small and does not cause the stars to twinkle.

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