Three musicians experiment with the Doppler effect. Musician A ri… - Vidyadip

MCQ

Three musicians experiment with the Doppler effect. Musician $A$ rides in a car at a speed $u$ directly away from musician $B$ who is stationary. Musician $C$ rides in a car directly toward $B$ and travels at the same speed as $A$ . Musician $A$ plays a note at frequency $f_A$ on his trumpet $B$ hears the note, adjusts his trumpet, and plays the same note he heard. Choose the incorrect statement

A
The note heard by $C$ coming from $B$ will be the same pitch as $f_A$
✓
The note heard by $A$ coming from $B$ will be higher in pitch than $f_A$
C
The note heard by $A$ coming from $B$ will be lower in pitch than $f_A$
D
The note heard by $B$ coming from $A$ will be lower in pitch than $f_A$

✓

Answer

Correct option: B.

The note heard by $A$ coming from $B$ will be higher in pitch than $f_A$

b
$\mathrm{f}_{\mathrm{B}}=\frac{\mathrm{c}}{\mathrm{c}+\mathrm{u}} \mathrm{f}_{\mathrm{A}}<\mathrm{f}_{\mathrm{A}}$

Heard by $Af_B^\prime = \frac{{c - u}}{c}{f_B} = \frac{{c - u}}{{c + u}}{f_A} < {f_A}$

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