Materials that let light pass through them?

Materials that allow most all light to pass through them are called transparent. Examples of transparent items are glass, water, and air. Those materials that allow some light to pass through them are called translucent and include things like frosted glass and wax paper.

They are transparent

Explanation:

Because they simple allow light to pass though instead of obstructing it

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me