ISRO2015-49

Question

What frequency range is used for microwave communications, satellite and radar?

• A. Low frequency$: 30$ kHz to $300$ kHz
• B. Medium frequency$: 300$ kHz to $3$ MHz
• C. Super high frequency$: 3000$ MHz to $30000$ MHz
• D. Extremely high frequency$: 30000$ kHz

Comments

option C) as per wiki range is 300 MHz - 300 GHz.

In C) we have 3 GHz - 30 GHz which is in range but D) is > 30 MHz

Answer 1

Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter; with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm). This broad definition includes both UHF and EHF (millimeter waves), and various sources use different boundaries.

so best answer is D

Answer 2

> Extremely high frequency - 3 × 10^7 Hz --(I)

> Range of Microwave radiation given on Wikipedia and quoted by another answer: 300 MHz to 300 GHz
-> 3 × 10^8 Hz to 3 × 10^11 Hz

We can observe from (I) that it fails to fall into this range. For option C however,

Super High Frequency - 3000 MHz to 30000 MHz
-> 3× 10^9 Hz to 3 × 10^10 Hz which is well within the frequency interval stated on Wikipedia.

Thus instead of (D), the answer should be (C).
Also, the question asks for a range, yet the answer refers to only a single frequency value. I believe the answer given by ISRO exam key is incorrect, and so are the other answers given for this question. It would be great if it can be verified by one of the super-seniors.

Thank You