Physics MCQs

14. 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
✅ The correct answer is option D.

16. 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, consequently the position of the image of a start changes with time
D. the light from the star is scattered by the dust particles and air molecules in the earth’s atmosphere
✅ The correct answer is option C.

18. Inside an aeroplane, flying at a high altitude,

A. the pressure is the same as that outside
B. normal atmospheric pressure is maintained by the use of air pumps
C. the pressure inside is less than the pressure outside
D. normal humidity and partial vacuum are maintained
✅ The correct answer is option B.