Assertion (A): A backward wave oscillator (BWO) has an internal positive feedback mechanism. Reason (R): Positive feedback is necessary for sustained oscillations. Which of the following is correct?

Introduction / Context:
A backward wave oscillator (BWO) is a type of vacuum tube oscillator that uses an electron beam interacting with a slow-wave structure. It is important to understand the role of feedback in generating oscillations.

Given Data / Assumptions:

• BWO principle: beam-wave interaction with backward wave propagation.
• Oscillations require feedback to reinforce the signal.

Concept / Approach:

In a BWO, internal positive feedback arises because the backward-traveling wave couples energy back to the electron beam. This feedback sustains oscillations. The reason statement correctly explains why oscillations persist: positive feedback is a fundamental requirement in all oscillators.

Step-by-Step Solution:

Verification / Alternative check:

Microwave device theory confirms BWOs operate on backward wave interaction providing feedback for self-oscillation.

Why Other Options Are Wrong:

• Option B: The explanation is indeed correct.
• Option C or D: deny correct parts.
• Option E: both statements are not wrong.

Common Pitfalls:

Confusing feedback in BWO with external cavity feedback in klystrons.

Final Answer:

Both A and R are correct, and R is the correct explanation of A