Two spaceships pass one another in opposite directions a a relative speed of 0.8c. an observer in spaceship 1 measures the length of spaceship 2 to be three fifths the length of her own ship. a) what is the ratio of the rest lengths of the two spaceships? b) what will an observer in spaceship 2 determine as the length of spaceship 1?

Ray 2 should cross through the focal point on the right side of the lens.

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.