Physics - Study Mode
[#636] The different colours of different stars are due to the variation of
Correct Answer
(A) Temperature
Explanation
Solution: The colour of a star – which varies from bluish-white and yellow to orange and red – is primarily due to its composition and effective temperature. And at all times, stars emit light which is a combination of several different wavelengths. On top of that, the colour of a star can change over time.
[#637] Which of the following is correct about the properties of Gravitational Forces?
Correct Answer
(B) They observe inverse square law
Explanation
Solution: It is a universal attractive force. It is directly proportional to the product of the masses of the two bodies. It obeys inverse square law. It is a long range force and does not need any intervening medium for its operation.
[#638] In the absence of the earth's atmosphere, sky would appear
Correct Answer
(D) Black
Explanation
Solution: Without an atmosphere the sky appears black, as evidenced by the lunar sky in pictures taken from the moon. But even a black sky has some lightness. At night, the sky always has a faint color, called "skyglow" by astronomers.
[#639] The fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
Correct Answer
(C) Johannes Kepler
Explanation
Solution: The fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by Johannes Kepler.
[#640] A bomb explodes on the moon. You will hear its sound on earth after ________
Correct Answer
(D) You cannot hear the sound of explosion
Explanation
Solution: As sound is produced due to vibrations in the medium particle, that is, it needs some medium for propagation and moon does not have any atmosphere. So ultimately, no medium for propagation of waves or vibrations of a medium particle.