81.
Echolocation is an adaptation bats use to

82.
Bats can sense obstacles because they produce

83.
A wavelength of 0.3 m is produced in air and it travels at a speed of 300 m/s. Then it will be an

85.
Velocity of sound in air does not depend on

86.
Speed of sound in air is unaffected by change in

87.
RADAR is used for

88.
What is the minimum distance (in metres) required to hear an echo?

90.
Which among the following determines the pitch of a sound?