UPSC Prelims 2011 Q57: Science & Technology – Computer & Information Technology
- (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
Answer: (a) Bluetooth uses 2.4 GHz radio frequency band, whereas Wi - Fi can use 2.4 GHz or 5 GHz frequency band
Explanation
The real difference between Bluetooth and Wi-Fi
Both are wireless technologies, but they differ in frequency bands and range/use-case.
| Option | Verdict | Reason |
|---|---|---|
| (a) Bluetooth uses 2.4 GHz only; Wi-Fi can use 2.4 GHz or 5 GHz | Correct | Bluetooth operates solely in the 2.4 GHz band, while Wi-Fi can use either 2.4 GHz or 5 GHz, giving it more flexibility and less interference risk |
| (b) Bluetooth is for WLAN only, Wi-Fi for WWAN only | Incorrect | This is backwards and wrong: Wi-Fi is typically used for WLAN (local networks); neither is standardly described as WWAN |
| (c) Bluetooth needs line of sight, Wi-Fi does not | Incorrect | Both technologies use radio waves and do not strictly require line of sight; this is a false distinction |
| (d) Statements (a) and (b) are both correct | Incorrect | Since (b) is wrong, this combined option fails |
Bluetooth vs Wi-Fi:
| Point | Bluetooth | Wi-Fi |
|---|---|---|
| Frequency | 2.4 GHz only | 2.4 GHz or 5 GHz |
| Range | Short (a few metres) | Longer (tens of metres+) |
| Typical use | Device pairing (headphones, etc.) | Local area networking (WLAN) |
Answer: (a) Bluetooth uses 2.4 GHz radio frequency band, whereas Wi-Fi can use 2.4 GHz or 5 GHz frequency band.
Why each option is right or wrong
- (a) CORRECT. Bluetooth is fixed at 2.4 GHz; Wi-Fi can operate on either 2.4 GHz or 5 GHz.
- (b) Incorrect. This WLAN/WWAN split is a fabricated distinction; Wi-Fi is the WLAN technology, not Bluetooth.
- (c) Incorrect. Neither Bluetooth nor Wi-Fi requires line of sight; both use omnidirectional radio waves.
- (d) Incorrect. Since statement (b) is factually wrong, this combined option cannot be correct.
Key point
The real Bluetooth/Wi-Fi difference: Bluetooth uses ONLY 2.4 GHz; Wi-Fi can use 2.4 GHz OR 5 GHz. Neither needs line of sight, and the WLAN/WWAN split in option (b) is false.
Remember
Bluetooth: 2.4 GHz only. Wi-Fi: 2.4 GHz or 5 GHz. Both are non-line-of-sight radio technologies.
Common mistakes
- Inventing a WLAN vs WWAN distinction between the two technologies that does not exist.
- Assuming either technology requires line of sight like infrared does.
- Not knowing Wi-Fi's dual-band (2.4/5 GHz) capability versus Bluetooth's single band.
Exam tip
Bluetooth = 2.4 GHz only. Wi-Fi = 2.4 or 5 GHz. Neither needs line of sight. Memorise this pairing precisely.
Sources
- Institute of Electrical and Electronics Engineers — IEEE 802.11: Standard for Wireless LAN Medium Access Control and Physical Layer Specifications
- Bluetooth Special Interest Group — Bluetooth Core Specification