A ray of light passes from glass into air at an angle of incidence of 40 degrees. The glass has a critical angle of 42 degrees. Which diagram shows what happened to the
ray?

A is correct

Refracted light is almost along the x-axis

Ni sin thetai = Nr sin thetar

In this case thetai is the incident angle and thetar the refracted angle

At the critical angle thetar = 90 deg and

1 = Ni sin thetai   since Nr is the refractive index of air  

Ni = 1 / sin 42 = giving Ni = 1.49 for the glass

the focus of lesson 1 is newton's first law of motion - sometimes referred to as the law of inertia. newton's first law of motion is often stated as. an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

explanation:

the part of the wave he is travelling on is the crest