2000 General Studies, all questions
UPSC Prelims 2000 · General Studies
Question 97: Science and Technology
A ‘black hole’ is a body in space which does not allow any radiation to come out. This property is due to its
avery small size
bvery large size
cvery high density
dvery low density
AnswerThe answer is (c).
A black hole is a body so dense that its gravity is extremely strong; the escape velocity at its surface is greater than the speed of light, so no radiation can escape. It forms when a massive star collapses. Size alone does not do it: it is the enormous mass packed into a very small volume, that is, very high density.
Why each option is right or wrong
- (a) Small size alone is not enough; it must come with enormous mass and so high density.
- (b) A very large size would lower the escape velocity, not raise it.
- (c) Right: very high density gives escape velocity above the speed of light.
- (d) Very low density would mean weak gravity, so radiation could escape.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2000, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.