JEE PYQ: Waves And Sound Question 35
Question 35 - 2019 (12 Apr Shift 2)
Two sources of sound $S_1$ and $S_2$ produce sound waves of same frequency 660 Hz. A listener is moving from source $S_1$ towards $S_2$ with a constant speed $u$ m/s and he hears 10 beats/s. The velocity of sound is 330 m/s. Then $u$ equals:
(1) 5.5 m/s
(2) 15.0 m/s
(3) 2.5 m/s
(4) 10.0 m/s
Show Answer
Answer: (3)
Solution
$f_1 = f \cdot \frac{v + v_0}{v}$ and $f_2 = f \cdot \frac{v + v_0}{v}$
But frequency,
$f_1 - f_2 = f \times \frac{2v_0}{v}$
or $10 = 660 \times \frac{2u}{330}$
$\therefore u = 2.5$ m/s.
BETA
