A bat moving at 10ms- 1 towards a wall sends a sound signal of 8000 textHz towards it. On reflection, it hears a sound of frequency f . The value of f in textHz is close to (. textspeed of sound=320 ms- 1.)

Question

A bat moving at 10ms- 1 towards a wall sends a sound signal of 8000 textHz towards it. On reflection, it hears a sound of frequency f . The value of f in textHz is close to (. textspeed of sound=320 ms- 1.) (A) 8258 (B) 8424 (C) 8000 (D) 8516

Tardigrade Admin · Accepted Answer

We can assume that reflected wave is due to image of textB coming with same speed in opposite direction Solution

Observer f= (v + 10/v - 10) × f0 = (320 + 10/320 - 10) × 8000 = (330/310) × 8000 = (33/31) × 8000 = 8516 Hz

Q. A bat moving at $10 m s^{- 1}$ towards a wall sends a sound signal of $8000 Hz$ towards it. On reflection, it hears a sound of frequency $f$ . The value of $f$ in $Hz$ is close to

$(speed of sound = 320 m s^{- 1})$

$8258$

$8424$

$8000$

$8516$

We can assume that reflected wave is due to image of $B$ coming with same speed in opposite direction

Observer
$f = \frac{v + 10}{v - 10} \times f_{0}$
$= \frac{320 + 10}{320 - 10} \times 8000$
$= \frac{330}{310} \times 8000$
$= \frac{33}{31} \times 8000$
$= 8516 Hz$

Q. A bat moving at 10ms−1 towards a wall sends a sound signal of 8000Hz towards it. On reflection, it hears a sound of frequency f . The value of f in Hz is close to (speed of sound=320ms−1)

8258

8424

8000

8516