When an object is kept opposite to an ultrasonic sensor, it reflects the waves. In case the object is water, does it reflect or not? How does one know?

  • Welcome. I fail to see what this has to do with the Internet of Things, so, like others, I am voting to close the question as being off-topic here. It might well be on topic on physics.stackexchange.com though – Mawg says reinstate Monica Aug 14 '19 at 7:00

It's not really clear what you are asking here, but if you mean can you use ultrasound to measure the distance to the surface of water then the answer is yes.

Ultrasound range finders are regularly used to check the depth in tanks.

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