Bats cannot see very well. To orient themselves during their night flights, they emit ultrasounds. We cannot hear these sounds. The ultrasonic waves falling on obstacles or preys get ‘reflected’ back and reach the sensitive ears of bats. Thus, they come to know what all is present around them and where their prey is. This concept is also used in shipping to determine the depth of the sea using a device called sonar. It comprises a sound transmitter, a receiver, and a clock. The time difference between sending and receiving sound waves is measured, which is used to calculate the depth of the sea.
