How is light used to make other form of transportations safer

Which is not a source of noise pollution? a)airplanes b)acid rain c)machines d)cars

What are similarities and differences between refraction, reflection, diffraction and absorption?

You are driving directly behind a pickup truck, going at the same speed as the truck. a crate falls from the bed of the truck to the road. (a) will your car hit the crate before the crate hits the road if you neither brake nor swerve? (b) during the fall, is the horizontal speed of the crate more than, less than, or the same as that of the truck?