Which of the following statements are correct?
(A) The electric field and magnetic field vectors of an electromagnetic wave are perpendicular to each other and also perpendicular to the direction of propagation of wave.
(B) Short waves are reflected from ionosphere.
(C) Electric field vector, E and magnetic field vector B have the same frequency.
(D) The line integral of magnetic field induction over a closed path is not zero.
Choose the correct answer from the options given below :
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A), (B) and (C) only
(A) The electric field and magnetic field vectors of an electromagnetic wave are perpendicular to each other and also perpendicular to the direction of propagation of wave. — Correct. An electromagnetic wave is transverse: \( \vec{E} \), \( \vec{B} \) and the direction of propagation \( \vec{E}\times\vec{B} \) are mutually perpendicular.
(B) Short waves are reflected from ionosphere. — Correct. Waves of a few MHz up to about 30 MHz are reflected back towards the earth by the ionosphere, which is how short-wave broadcasts reach distant places.
(C) Electric field vector, E and magnetic field vector B have the same frequency. — Correct. \( \vec{E} \) and \( \vec{B} \) are two parts of the same wave: they oscillate with the same frequency and in phase.
(D) The line integral of magnetic field induction over a closed path is not zero. — Incorrect. The property that holds for the magnetic field is Gauss’s law for magnetism: magnetic field lines form closed loops, so the net magnetic flux through any closed surface is zero.
\( \displaystyle \oint \vec{B}\cdot d\vec{A} = 0 \)
The statement, as given, is not this standard result, so it is not accepted as correct.
Note: Statements (A) and (C) of this question are from the latest textbook (2026-27). Statement (B), that short waves are reflected from the ionosphere, is printed only in the pre-rationalised textbook (2022-23). It was removed from the latest book, and it also appears to be out of the CUET 2026 syllabus.
NCERT (2026-27):
Nature of Electromagnetic Waves – “It can be shown from Maxwell’s equations that electric and magnetic fields in an electromagnetic wave are perpendicular to each other, and to the direction of propagation.”
Nature of Electromagnetic Waves – “… We can write Ex and By as follows:
\( \displaystyle E_x = E_0 \sin(kz - \omega t) \qquad [8.7(a)] \)
\( \displaystyle B_y = B_0 \sin(kz - \omega t) \qquad [8.7(b)] \)”
NCERT (Pre-rationalised edition, 2022-23):
Sky Waves – “In the frequency range from a few MHz up to 30 to 40 MHz, long distance communication can be achieved by ionospheric reflection of radio waves back towards the earth. This mode of propagation is called sky wave propagation and is used by short wave broadcast services.”