UPSC Prelims 2008 · General Studies
Question 44: Science and Technology
Consider the following statements:
- 1.The albedo of an object determines its visual brightness when viewed with reflected light.
- 2.The albedo of Mercury is much greater than the albedo of the Earth.
Which of the statements given above is/are correct?
AnswerThe answer is (a).
Albedo is the fraction of incoming light that a surface reflects, so it decides how bright an object looks in reflected light; statement 1 is correct. Statement 2 is wrong: Mercury is dark and rocky, with an albedo of about 0.1 or less, while Earth reflects roughly 30 per cent of sunlight because of clouds, ice and oceans. Earth's albedo is greater than Mercury's.
- 1. Albedo is the share of light reflected, which sets brightness in reflected light.
- 2. Mercury's albedo is much lower than Earth's.
How you could have got this
- If you were sure statement 1 is correct, (b) and (d) go: each of them leaves 1 out.
What you needed to know: Albedo is the share of light reflected, which sets brightness in reflected light.
- Then, if you were sure statement 2 is not correct, (c) goes: it includes 2.
What you needed to know: Mercury's albedo is much lower than Earth's.
Only (a) is left. This one needs every statement.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Statement 1 is right and statement 2 is wrong.
- (b) Statement 2 is wrong, since Earth's albedo is greater than Mercury's.
- (c) Statement 2 is wrong, so both cannot be correct.
- (d) Statement 1 is correct, so neither being correct is wrong.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2008, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.