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: Evaluate Assertion (A).
Electromagnetic (EM) waves are composed of fluctuating electric and magnetic fields that can traverse a vacuum, as delineated by Maxwell’s equations. Unlike mechanical waves, which necessitate a medium, EM waves do not require one for propagation (e.g., light traversing space). Consequently, Assertion (A) is accurate.Step 2: Evaluate Reason (R).
EM waves are classified as transverse waves because their electric and magnetic fields oscillate perpendicularly to their direction of propagation. For instance, if an EM wave advances along the \( z \)-axis, the electric field might oscillate along the \( x \)-axis and the magnetic field along the \( y \)-axis. This characteristic is fundamental to EM waves, thus Reason (R) is accurate.Step 3: Determine if Reason (R) substantiates Assertion (A).
The capacity of EM waves to propagate without a medium stems from their self-sustaining nature as oscillations of electric and magnetic fields, not from their transverse wave property. Mechanical transverse waves (e.g., waves on a string) depend on a medium, illustrating that being transverse does not inherently negate the need for a medium. Therefore, although both statements are true, Reason (R) does not provide a correct explanation for Assertion (A).Step 4: Conclude.
Both Assertion (A) and Reason (R) are verified as true. However, Reason (R) does not correctly explain Assertion (A). Accordingly, the appropriate selection is (B).