Arrange the following devices used to detect the electromagnetic waves according to their frequencies in descending order.
(A) Thermopiles
(B) Geiger tubes
(C) Point contact diodes
(D) Photocells
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (B), (D), (A), (C)
Each device detects a different part of the electromagnetic spectrum; arranging the devices by frequency means arranging those parts.
Geiger tubes: gamma rays and X-rays (highest frequency)
Photocells: visible light and ultraviolet
Thermopiles: infrared (heat radiation)
Point contact diodes: microwaves (lowest frequency)
In descending order of frequency: gamma/X-rays > visible/UV > infrared > microwaves, that is, (B), (D), (A), (C).
NCERT (2026-27):
Gamma Rays – …
