Some wireless communications are given as following. Select the correct arrangement of them into their increasing order of frequencies from low to high band range.
A. Satellite communication
B. Sky wave communication
C. A.M. Broad Cast
D. F.M. Broad Cast
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → C → B → D → A
Each service uses a typical frequency band: medium-wave AM broadcast is the lowest, sky waves reflected by the ionosphere work only up to about 30 MHz, FM uses VHF, and satellite communication uses the GHz range so that the waves pass through the ionosphere.
(C) A.M. Broad Cast — \( \approx 540\text{ to }1600\,\mathrm{kHz} \)
(B) Sky wave communication — \( \approx 3\text{ to }30\,\mathrm{MHz} \)
(D) F.M. Broad Cast — \( \approx 88\text{ to }108\,\mathrm{MHz} \)
(A) Satellite communication — a few GHz
So the increasing order of frequency is C → B → D → A.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Bandwidth of Transmission Medium – “… This range of frequencies is further subdivided and allocated for various services as indicated in Table 15.2.”
Summary – “… 9. Long distance communication between two points on the earth is achieved through reflection of electromagnetic waves by ionosphere. Such waves are called sky waves. Sky wave propagation takes place up to frequency of about 30 MHz.”
