1999 General Studies, all questions
UPSC Prelims 1999 · General Studies
Question 118: Science and Technology
Barium in a suitable form is administered to patients before an X-ray examination of the stomach, because
abarium allows X-rays to pass through the stomach on account of its transparency to X-rays
bbarium compound, like magnesium sulphate helps in cleaning the stomach before X-ray examination
cbarium is a good absorber of X-rays and this helps the stomach to appear clearly in contrast with the other regions in the picture
dbarium salts are white in colour and this helps the stomach to appear clearly in contrast with other regions in the picture
AnswerThe answer is (c).
Barium sulphate is a good absorber of X-rays, so when a patient swallows a barium meal it coats the lining of the stomach and shows up as a clear white outline against the surrounding soft tissue, which X-rays pass through more easily. Barium is not transparent to X-rays, and its colour does not matter. Remember: barium absorbs X-rays and so gives contrast.
Why each option is right or wrong
- (a) Wrong. Barium absorbs X-rays; it is not transparent to them.
- (b) Wrong. Barium does not clean the stomach; magnesium sulphate is a purgative.
- (c) Right. Barium absorbs X-rays, giving contrast.
- (d) Wrong. The colour of the salt has no effect on an X-ray picture.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1999, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.