UPSC Prelims 2020 · GS Paper I
Question 39: Science and Technology
With reference to Visible Light Communication (VLC) technology, which of the following statements are correct ?
- 1.VLC uses electromagnetic spectrum wavelengths 375 to 780 nm.
- 2.VLC is known as long-range optical wireless communication.
- 3.VLC can transmit large amounts of data faster than Bluetooth.
- 4.VLC has no electromagnetic interference.
Select the correct answer using the code given below :
AnswerUPSC’s answer is (c).
Visible light communication uses wavelengths of about 375 to 780 nm, the visible band, so statement 1 holds. It is a short-range optical wireless technology, not long-range, so statement 2 is wrong. It can carry data much faster than Bluetooth, as in Li-Fi, and because it uses light rather than radio waves it causes no electromagnetic interference.
- 1. The visible spectrum is roughly 375 to 780 nm.
- 2. VLC is a short-range optical wireless technology.
- 3. It can carry data faster than Bluetooth.
- 4. It uses light, so there is no radio-frequency interference.
How you could have got this
- If you were sure statement 2 is not correct, (a), (b) and (d) go: each of them includes 2.
What you needed to know: VLC is a short-range optical wireless technology.
Only (c) is left. You didn’t need statements 1, 3 or 4.
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) Wrong: statement 2 is false because VLC is short-range.
- (b) Wrong: statement 2 is false, and statement 3 is true.
- (c) Right: statements 1, 3 and 4.
- (d) Wrong: statement 2 is false and statement 1 is true.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper I, Series A. The paper on upsc.gov.in.