Which of the following statements about electromagnetic waves is/are correct?
A. Visible Light can be polarised but X-rays cannot.
B. X-rays in vacuum travel faster than visible light waves in vacuum.
C. The energy of X-ray photon is greater than that of a visible light photon.
D. Radio waves are produced by the accelerated motion of charges in conducting wires.
E. An electric dipole is a basic source of electromagnetic waves.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → C, D and E only
All electromagnetic waves are transverse waves of oscillating electric and magnetic fields, produced by accelerated charges, and all travel in vacuum with the same speed c.
(A) Visible Light can be polarised but X-rays cannot. — Incorrect. X-rays are transverse too, so they can also be polarised.
(B) X-rays in vacuum travel faster than visible light waves in vacuum. — Incorrect. Every electromagnetic wave travels at \( c = 3\times10^{8}\,\mathrm{m\,s^{-1}} \) in vacuum.
(C) The energy of X-ray photon is greater than that of a visible light photon. — Correct. X-rays have a much higher frequency, and \( E = h\nu \).
(D) Radio waves are produced by the accelerated motion of charges in conducting wires. — Correct. This is how a transmitting antenna works.
(E) An electric dipole is a basic source of electromagnetic waves. — Correct. An oscillating electric dipole radiates electromagnetic waves at its frequency of oscillation.
NCERT (2026-27):
Radio Waves – “Radio waves are produced by the accelerated motion of charges in conducting wires.”
Summary – “… An electric charge oscillating harmonically with frequency ν, produces electromagnetic waves of the same frequency ν. An electric dipole is a basic source of electromagnetic waves.”
Points to Ponder – “1. The basic difference between various types of electromagnetic waves lies in their wavelengths or frequencies since all of them travel through vacuum with the same speed.”