Question A siren is moving past Mary as she sits stuck in traffic. To Mary, the pitch of
the siren changes as it passes her position. What causes this to happen?
A. The energy of the wave increased as the siren passed Mary's
location.
B. The frequency of the sound the siren makes changes as it passes
Mary
C. The sound waves in front of the siren bunch up, and those behind
the siren spread out.
D. The amplitude of the sound waves in front of the siren are larger
than those behind the siren.
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