UPSC Prelims 2008 · General Studies

Question 111: Science and Technology

Which one of the following laser types is used in a laser printer?

aDye laser

bGas laser

cSemiconductor laser

dExcimer laser

AnswerThe answer is (c).

Modern laser printers use a semiconductor (diode) laser, which is small, cheap and can be switched on and off very quickly. The beam is swept across a charged drum, discharging the spots that will pick up toner; the toner is then transferred to paper and fused by heat. Dye and excimer lasers serve other uses, and gas lasers are bulkier.

Why each option is right or wrong

(a) Dye lasers are bulky tunable lasers used in research.
(b) Gas lasers such as helium-neon were used in early printers, but modern ones use diodes.
(c) A semiconductor laser is used in a laser printer.
(d) Excimer lasers are used in eye surgery and chip-making.

Explanation: written by UPSC Grade, not by UPSC.

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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.