UPSC Prelims 1999 · General Studies
Question 119: Science and Technology
Endoscopy, a technique used to explore the stomach or other inner parts of the body is based on the phenomenon of
AnswerThe answer is (a).
Endoscopy uses a bundle of optical fibres. Light entering one end is carried along the fibre by repeated total internal reflection at the boundary between the core and its outer layer, even round bends, so the doctor can light up and view the inside of the stomach or other organs. Interference, diffraction and polarisation are not the basis. Remember: optical fibres work by total internal reflection.
Why each option is right or wrong
- (a) Right. Total internal reflection carries light along the fibres.
- (b) Wrong. Interference is not involved.
- (c) Wrong. Diffraction is not involved.
- (d) Wrong. Polarisation is not involved.
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.