Which among the following statement are correct?
A. Ultraviolet rays can be detected with a photocell.
B. X-rays are detected with ionisation chamber
C. Visible light is detected with a thermopile
D. Gamma rays are detected with point contact diodes
E. Infrared rays are detected with a bolometer
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A, B and E only
Each part of the electromagnetic spectrum is detected by a device that responds to that kind of radiation: photoelectric devices for high-frequency light, ionisation for X-rays and gamma rays, and heating effects for infrared.
(A) Ultraviolet rays can be detected with a photocell. — Correct. Ultraviolet photons have enough energy to eject electrons, so photocells and photographic film detect them.
(B) X-rays are detected with ionisation chamber — Correct. X-rays ionise the gas in the chamber; photographic film and Geiger tubes are also used.
(C) Visible light is detected with a thermopile — Incorrect. A thermopile works on the heating effect and is a detector of infrared; visible light is detected by the eye, photocells and photographic film.
(D) Gamma rays are detected with point contact diodes — Incorrect. Point contact diodes detect microwaves; gamma rays are detected through the ionisation they produce.
(E) Infrared rays are detected with a bolometer — Correct. Infrared radiation heats the sensing element, and the change in its resistance is measured; thermopiles are used in the same way.
Statements A, B and E are correct, which is Option (2).
NCERT (2026-27):
Gamma Rays – …
