Assertion–Reason (standing waves): Assertion (A): Two equal-amplitude waves traveling in opposite directions on a uniform line combine to form a standing wave. Reason (R): The ratio of the maximum to the minimum value of the standing-wave envelope is called the standing-wave ratio (SWR).

Introduction / Context:
Standing waves arise from reflections on transmission lines and waveguides. Recognizing both the formation mechanism and the definition of SWR helps in matching networks and power-transfer optimization.

Given Data / Assumptions:

• Lossless or low-loss line for conceptual clarity.
• Two counter-propagating waves of equal amplitude.
• Linear superposition holds.

Concept / Approach:

Adding equal forward and reverse waves yields a stationary pattern with fixed nodes and antinodes. SWR quantifies the severity of standing waves as SWR = V_max / V_min. Although both statements are true, the definition of SWR does not explain why standing waves form; reflection and superposition do.

Step-by-Step Solution:

Verification / Alternative check:

Slotted-line measurements reveal λ/2 spacing between adjacent minima and enable SWR extraction from measured V_max and V_min, independent of the causative explanation.

Why Other Options Are Wrong:

• A only or R only: incomplete; both are standard facts.
• “R explains A”: incorrect because standing waves result from reflection, not from the SWR definition.
• Both wrong: contradicts line theory.

Common Pitfalls:

Confusing a metric (SWR) with the physical phenomenon (interference). Equal amplitudes produce the most pronounced standing wave; unequal amplitudes still form standing waves but with smaller SWR.

Final Answer:

Both A and R are correct but R is not correct explanation of A