See what I did with the title there? I'm so clever.
So, echos. An echo happens when you say something or make a noise and the sound waves from your mouth bounce off a hard surface and rebound back to you, which is why you hear what you said again and again and again. This is why echoes are common in caves, because you're surrounded by hard surfaces.
We know that when a wave reaches the end of its medium, it undergoes a certain process depending on how it's medium ends. Transmission/refraction, diffraction, and the one that causes echoes: reflection.
Awhile ago I stumbled upon something really cool involving echolocation, which is the ability to make sounds and determine where and sometimes what certain objects are in a room. I watched an especially awe-inspiring video, showing blind people that had learned to use echolocation; an object was placed on a big table in front of them, and by making clicking noises with their mouths, they were able to determine where on the table it was placed and even what shape it was. Some even guessed the objects.
I wish I could link the video, but since I can't I do hope you'll try to look it up and maybe someone can find it. I thought that was pretty amazing, to be able to see in a completely new way. Yet another awesome application of physics.
Until next time,