Question

sound cannot propagate through a vacuum. why how is echo heard ?​

Answer 1

Answer:

Sound cannot travel through a vacuum. A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in.

An echo is a sound that is repeated because the sound waves are reflected back. Sound waves can bounce off smooth, hard objects in the same way as a rubber ball bounces off the ground. ... That is why echoes can be heard in a canyon, cave, or mountain range.

Explanation:

Answer 2

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Sound cannot travel through a vacuum. A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in.

An echo is a sound that is repeated because the sound waves are reflected back. Sound waves can bounce off smooth, hard objects in the same way as a rubber ball bounces off the ground. That is why echoes can be heard in a canyon, cave, or mountain range.