Question

Assertion (A): EM waves do not require a medium for their propagation.
Reason (R): EM waves are transverse waves.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Both Assertion (A) and Reason (R) are false.

Hint:

EM waves propagate without a medium due to their self-sustaining electric and magnetic fields, as per Maxwell’s equations. Their transverse nature (oscillations perpendicular to propagation) is a separate property and not the reason for medium-less propagation.

Answer 1

The Correct Option is B

Step 1: Analyze Assertion (A).
Electromagnetic (EM) waves consist of oscillating electric and magnetic fields that can propagate through a vacuum, as described by Maxwell’s equations. Unlike mechanical waves, which require a medium, EM waves do not need a medium to travel (e.g., light travels through space). Thus, Assertion (A) is true. Step 2: Analyze Reason (R).
EM waves are transverse waves because their electric and magnetic fields oscillate perpendicular to the direction of propagation. For example, if an EM wave propagates along the \( z \)-axis, the electric field may oscillate along the \( x \)-axis and the magnetic field along the \( y \)-axis. This is a defining characteristic of EM waves, so Reason (R) is true. Step 3: Check if Reason (R) explains Assertion (A).
The ability of EM waves to propagate without a medium is due to their nature as self-sustaining oscillations of electric and magnetic fields, not because they are transverse. Mechanical transverse waves (e.g., on a string) require a medium, showing that being transverse does not imply no medium is needed. Thus, while both statements are true, Reason (R) does not explain Assertion (A). Step 4: Conclusion.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A), so the correct option is (B).