What is the law of reflection, and does it apply to all reflecting surfaces?

Avery hard rubber ball (m = 0.5 kg) is falling vertically at 4 m/s just before it bounces on the floor. the ball rebounds back at essentially the same speed. if the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?

What happens to the light rays when they hit the specimen?

Why is it important always to use horizontal bars in unit fractions when performing unit conversions?