For my electronic project, I have been searching the internet for a non invasive flow meter that does not require disassembly. I have found an ultrasonic measurement technique that use the clamp on method (just fitting on to the pipe) for flow measurement of liquid though a pipe. But when I search through internet I found that ultrasound can behave like light as it is reflected back from a solid surface. Is this true? Or it is like ordinary sound that can pass through a medium?
Ultrasound partially reflects when it encounters a medium with different acoustic impedance. It behaves like light and obeys Fresnel equations. If the angle of incidence is smaller than the total internal reflection angle, then part of the ultrasound beam will go forward (with some refraction) and part will reflect back from the interface between the media. The greater the difference between acoustic impedance of the two, the more the ultrasound will bounce back.