Question

What is echo? Give two application of ultrasound

Answer 1

The bouncing back of sound is known as echo. The two applications are :
Diagnostic imaging technique.
To point some thing . like bat sends ultrasound to point some thing

Answer 2

the repitation of sound is known as echo...
application --
1. the ultrasound waves are used to form an image of the heart using reflection and detection  of these waves from various parts. 
2. medical ultrasound  is a diagnostic imaging technique  based on ultrasound