Which of the following is not part of electromagnetic spectrum?

The correct answer is Option (1) → \( \alpha \) rays

The electromagnetic spectrum consists of waves of oscillating electric and magnetic fields travelling at the speed of light: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.

\( \alpha \) rays are streams of helium nuclei (two protons and two neutrons), that is, charged material particles, not electromagnetic waves. So they are not part of the electromagnetic spectrum.

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. The classification of em waves according to frequency is the electromagnetic spectrum (Fig. 8.4).”