2007 General Studies, all questions
UPSC Prelims 2007 · General Studies
Question 112: Science and Technology
Which one of the following types of glass can cut off ultraviolet rays?
aSoda glass
bPyrex glass
cJena glass
dCrookes glass
AnswerThe answer is (d).
Crookes glass, which contains cerium oxide among its ingredients, absorbs ultraviolet rays and is used in sunglasses and spectacles. Soda glass is ordinary window glass, Pyrex is a heat-resistant borosilicate glass, and Jena glass is a hard, heat-resistant laboratory glass. Remember: Crookes glass means UV protection.
Why each option is right or wrong
- (a) Soda glass is common glass, used for bottles and windows.
- (b) Pyrex resists heat, but is not the UV-absorbing glass.
- (c) Jena glass is a hard laboratory glass.
- (d) Correct: Crookes glass cuts off ultraviolet rays.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2007, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.