• A ray of light is traveling in a glass cube that is totally im-
mersed in water. You find that if the ray is incident on the glass–water
interface at an angle to the normal larger than 48.7°, no light is refracted
into the water. What is the refractive index of the glass?
Point charges q= 50 μC and 92=-25C are
placed 1.0 m apart. What is the force on a third charge 93= 20 μC placed midway between 1 and 4₂?