JEE PYQ: Waves And Sound Question 5
Question 5 - 2021 (24 Feb Shift 2)
Two cars are approaching each other at an equal speed of 7.2 km/hr. When they see each other, both blow horns having frequency of 676 Hz. The beat frequency heard by each driver will be __________ Hz. [Velocity of sound in air is 340 m/s.]
Show Answer
Answer: 8
Solution
Speed $= 7.2$ km/h $= 2$ m/s
Frequency as heard by A: $f_A’ = f_D\left(\frac{V + V_0}{V - V_s}\right)$
$f_A’ = 676\left(\frac{340 + 2}{340 - 2}\right)$
$f_A’ = 684$ Hz
$\therefore f_{\text{Beat}} = f_A’ - f_B$
$= 684 - 676$
$= 8$ Hz
BETA
