Set 4: Command of Evidence (Intermediate)

Explanation

Answer: A

PASSAGE

Doppler effect: approaching siren sounds higher (compressed waves), receding sounds lower (stretched waves).

Why does pitch change?

A. Siren's actual frequency changes.✓ Correct

B. Movement compresses/stretches perceived waves.

C. Ears become less sensitive.

D. Driver adjusts siren.

Detailed Explanation

Waves are 'compressed' or 'stretched' by movement.

Why others are wrong:

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