Which rule correctly describes the direction of refraction when light moves from a slower to a faster medium?

• A. Towards normal: fast to slow, small n to big n
• B. Away from normal: slow to fast, big n to small n
• C. Parallel to the normal regardless of speeds
• D. It reverses the direction of travel

Answer: (B)

When light passes from one medium to another, its speed changes and the path bends according to Snell’s law: n1 sin theta1 = n2 sin theta2. If you move from a slower medium (higher refractive index) to a faster one (lower refractive index), the speed increases in the second medium. To keep the same component of the wave’s direction parallel to the interface, the angle with the normal must increase, so the refracted ray bends away from the normal. That means the ray travels more obliquely relative to the normal after entering the faster medium.

So the correct rule is that the direction of refraction is away from the normal when light goes from slower to faster. This contrasts with moving into a slower medium, where it would bend toward the normal. The other statements don’t correctly describe this relationship or the geometric change in direction.