What happens to light as it moves at an angle into a medium that has a lower index of refraction?

a. it speeds up, and the angle increases.
b. it speeds up, and the angle decreases.
c. it slows down, and the angle decreases.
d. it slows down, and the angle increases.

Two carts, one of mass 2m and one of mass m, approach each other with the same speed, v. when the carts collide, they hook together. assume that positive momentum is to the right. which graph best represents the momentum of both carts over time, before and after the collision?