N° 6 : Bats produce sound waves of 50000 to 200000 vibrations per second These waves hit the obstacles and an echo that is extremely accurate returns. Bats capture the echo with their very
sensitive and developed ears: as a result they know the position of the obstacle precisely.
1) a) Pick up the domain of frequencies emitted by the bat in Hz.
b) Are these waves audible by the human ear ? Why?
from the text the sentence which mentions a physical phenomenon.
c) Pick
up
2) A bat sends a wave of 100 kHz towards an
obstacle situated at a distance d = 2 m and
receives the echo after a time «t».
Given that the speed of sound waves in air
)
Obstacle
330 m/s.
a) Calculate the period and the wavelength of
the waves emitted in air.
b) Find the distance « D » covered by the wave after leaving the bat and till its return to the bat.
c) Deduce, in ms, the duration (emission - reception) denoted by «t».​