Question

Planets do not twinkle because

• A. they emit light of a constant intensity
• B. their distance from the earth does not change with time
• C. they are very far away from the earth resulting in decrease in intensity of light
• D. they are nearer to earth and hence we receive a greater amount of light and, therefore minor variations in the intensity are not noticeable

Answer 1

The correct option is D they are nearer to earth and hence we receive a greater amount of light and, therefore minor variations in the intensity are not noticeable

Planets do not seem to twinkle like stars, although light coming from them also passes through the variable refractive index of the atmosphere. This is because stars appear as point objects to us due to their enormous distance from the earth.

On the other hand, planets are quite close to the earth, therefore, they are more like extended objects and can be considered as a collection of a large number of point-sized sources of light. Light from different parts of the planet form an image in the eye. There are fluctuations in the brightness for different parts of the planet but these fluctuations occur at different times for different parts of the same planet.

Thus, the total variation in the amount of light entering our eye or the intensity of light from all these parts average out to be zero. Therefore, to the eye the planets do not twinkle.

Hence, the correct answer is OPTION D.