Question

What should be the minimum distance to the reflecting surface is the velocity of sound in air is 340 m/s ?

Answer 1

$\Longrightarrow{\boxed{\bold{Answer : d \geq 17\:m}}}$

$\textbf{\underline{Step-by-step explanation :- }}$

Since the sound travels twice, one from source to object and then from object to source.

Therefore for them distance is twice.

s = 2d / t

340 m/s = 2d / t

d = 340t / 2 = 170t

Now, to hear echo time must be $\bold{\geq 0.1\:s }$

$\bold{ d \geq 170 \times 0.1 }$

$\boxed{\bold{ d \geq 17 m }}$

Answer 2

here is your answer ☺☺☺☺☺☺☺




we know that sound have to travel, from listener to reflector then to listener

so total distance travelled = 2d

now, distance = speed× time = 340 ×0.1

=2d = 34

=d = 17 m

minimum distance for echo is 17 m