UPSC Civil Services Examination, Previous Year Questions (PYQs)
Q. With reference to ‘LiFi’, recently in the news, which of the following statements is/are correct? (2016)
- It uses light as the medium for high speed data transmission.
- It is a wireless technology and is several times faster than ‘WiFi’.
Select the correct answer using the code given below:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Ans: (c)
- Li-Fi stands for Light Fidelity and is a Visible Light Communications (VLC) system which runs wireless communications that travels at very high speeds. The term was coined by University of Edinburgh Professor Harald Haas during a TED Talk in 2011. Haas envisioned light bulbs that could act as wireless routers.
- Wi-Fi technology uses radio waves for transmission, whereas Li-Fi utilizes light waves. Wi-Fi works well for general wireless coverage within the building/ campus/compound, and Li-Fi is ideal for high density wireless data coverage in a confined area or room and is free from interference issues unlike the Wi-Fi. Speed of data transmission for Li-Fi is approximately 1 Gbps and for Wi-Fi – IEEE 802.11n is approximately 150 Mbps. Hence, statements 1 and 2 are correct.
- Therefore, option (c) is the correct answer.
Q. What is the difference between Bluetooth and Wi-Fi devices? (2011)
(a) Bluetooth uses 2.4 GHz radio frequency band whereas Wi-Fi can use 2.4 GHz or 5 GHz frequency band
(b) Bluetooth is used for Wireless Local Area Networks (WLAN) only, whereas Wi-Fi is used for Wireless Wide Area Networks (WWAN) only
(c) When information is transmitted between two devices using Bluetooth technology, the devices have to be in the line of sight of each other, but when Wi-Fi technology is used the devices need not be in the line of sight of each other
(d) The statements (a) and (b) given above are correct in this context
Ans: (a)
Q. Consider the following: (2010)
- Bluetooth device
- Cordless phone
- Microwave oven
- Wi-Fi device
Which of the above can operate between 2.4 and 2.5 GHz range of radio frequency band?
(a) 1 and 2 only
(b) 3 and 4 only
(c) 1, 2 and 4 only
(d) 1, 2, 3 and 4
Ans: (d)
- Bluetooth is a wireless technology for exchanging data between fixed and mobile devices over short distances. The working frequency band is 2.400 to 2.485 GHz. Hence, 1 is correct.
- A cordless telephone works in the frequency band of 2.4 GHz and 5.8 GHz. Hence, 2 is correct.
- Microwave oven uses frequencies of 2.45 GHz. Hence, 3 is correct.
- Wi-Fi is technology for radio wireless local area networking of devices. Wi-Fi most commonly uses the 2.4 GHz band. Hence, 4 is correct.
- Therefore, option (d) is the correct answer.
