Select the correct pair stating has applications of reflection of sound waves.

Explanation

(a) Stethoscope: It works on the principle of multiple reflections. It consists of three main parts: (i) Chest piece (ii) Ear piece (iii) Rubber tube
(b) Echo: An echo is a repetition of sound produced by the reflection of sound waves from a wall, mountain or other obstructing surfaces. The speed of sound in air at `20^(@)C` is 344 ms. If we shout at a wall which is at 344 m away, then the sound will take 1 second to reach the wall. After reflection, the sound will take one more second to reach us. Therefore, we hear the echo after two seconds.
(c) SONAR: Sound Navigation and Ranging. Sonar systems make use of reflections of sound waves in water to locate the position or motion of an object. Similarly, dolphins and bats use the sonar principle to find their way in the darkness.