Which of the following is NOT em wave?

The correct answer is Option (4) → Cathode rays

An electromagnetic wave is made of oscillating electric and magnetic fields and travels through vacuum at the speed of light. Its sources are accelerated charges and transitions in atoms and nuclei.

Cathode rays are a stream of fast-moving electrons, which have mass and charge and are deflected by electric and magnetic fields. They are particles, not electromagnetic waves, while X-rays, gamma rays and microwaves are all parts of the electromagnetic spectrum.

Note: The same question was also asked in CUET (UG) 2023 on 09-06-2023 (Slot 3).

NCERT (2026-27):
Introduction – “… These cathode rays were discovered, in 1870, by William Crookes who later, in 1879, suggested that these rays consisted of streams of fast moving negatively charged particles.”