Which of the following are not electromagnetic waves?
A. Gamma rays
B. Cathode rays
C. X-rays
D. \( \beta \)-rays
E. Radio waves
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → B and D only
An electromagnetic wave is a disturbance of oscillating electric and magnetic fields travelling at the speed of light. A beam of particles is not such a wave, even if it is fast.
(A) Gamma rays — Electromagnetic. They are photons of the shortest wavelengths, emitted by nuclei.
(B) Cathode rays — Not electromagnetic. They are streams of electrons.
(C) X-rays — Electromagnetic. They lie between the ultraviolet and the gamma rays in the spectrum.
(D) \( \beta \)-rays — Not electromagnetic. They are fast electrons (or positrons) emitted in beta decay.
(E) Radio waves — Electromagnetic. They are the longest-wavelength electromagnetic waves.
NCERT (2026-27):
Electromagnetic Spectrum – “… We now know that, electromagnetic waves include visible light waves, X-rays, gamma rays, radio waves, microwaves, ultraviolet and infrared waves.”