UPSC Prelims 2010 · General Studies
Question 13: Science and Technology
Consider the following :
- 1.Bluetooth device
- 2.Cordless phone
- 3.Microwave oven
- 4.Wi-Fi device
Which of the above can operate between 2·4 and 2·5 GHz range of radio frequency band ?
AnswerThe answer is (d).
The 2.4 to 2.5 GHz band is the globally open ISM (industrial, scientific and medical) band, which needs no licence. Bluetooth devices, cordless phones and Wi-Fi all operate there, and a domestic microwave oven radiates at about 2.45 GHz, which is why it can interfere with Wi-Fi and Bluetooth. All four items qualify. Remember: Bluetooth, Wi-Fi, cordless phones and microwave ovens share the 2.4 GHz band.
- 1. Bluetooth uses the 2.4 GHz ISM band.
- 2. Many cordless phones operate at 2.4 GHz.
- 3. Domestic microwave ovens work at about 2.45 GHz.
- 4. Wi-Fi commonly uses 2.4 GHz channels.
How you could have got this
- If you were sure statement 1 is correct, (b) goes: it leaves 1 out.
What you needed to know: Bluetooth uses the 2.4 GHz ISM band.
- Then, if you were sure statement 3 is correct, (a) and (c) go: each of them leaves 3 out.
What you needed to know: Domestic microwave ovens work at about 2.45 GHz.
Only (d) is left. You didn’t need statements 2 or 4.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
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) Omits the microwave oven and Wi-Fi, which also work in this band.
- (b) Omits Bluetooth and cordless phones, which also work in this band.
- (c) Omits the microwave oven, which radiates at about 2.45 GHz.
- (d) Right: all four use the 2.4-2.5 GHz band.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.