A bus is moving with a velocity of \(5 \mathrm{~m} / \mathrm{s}\) towards a wall. The driver blows the horn of frequency \(165 \mathrm{~Hz}\). If the speed of sound in air is \(335 \mathrm{~m} / \mathrm{s}\), then after reflection of sound wave, the number of beats per second heard by the passengers in the bus will be

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.