The sources of electromagnetic radiations are:
A. Radioactive decay of the nucleus
B. Electron jumping from its outer orbit to inner orbit
C. Charges in uniform motion
D. Vibration of atoms and molecules
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A, B and D only
Electromagnetic waves are produced by accelerated charges, and by atoms and nuclei dropping to lower energy states. A charge moving with constant velocity produces steady fields but no radiation.
(A) Radioactive decay of the nucleus — Correct. A nucleus left in an excited state after a decay drops to a lower level and emits a gamma-ray photon.
(B) Electron jumping from its outer orbit to inner orbit — Correct. The energy difference between the two orbits is emitted as a photon (infrared, visible, ultraviolet or X-ray).
(C) Charges in uniform motion — Incorrect. A charge in uniform motion is not accelerated, so it does not radiate.
(D) Vibration of atoms and molecules — Correct. The vibration of atoms and molecules in hot bodies emits infrared radiation.
NCERT (2026-27):
Sources of Electromagnetic Waves –
