What is the physical meaning of the vertical intercept for the static frictional force vs. normal force graph?

Sounds propagates through some kind of medium. usually it's air, but it goes just as well through solid objects like walls, windows etc. a soundwave will compress the (air)molecules in front of it, and if this increased density wave hits your ears, you register it as sound. solid objects like walls are a lot denser than air, this means that they will damp a wave, but also carry it easier.

The fuzzy edges of shadows are a result of  diffraction 

All u need to do is see how 50cm work with each other