When light travels from a more refractive material to a less refractive material, how does the refracted ray bend?

• A. It bends toward the normal
• B. It bends away from the normal
• C. It travels straight
• D. It is totally reflected

Answer: (B)

When light crosses from a denser (more refractive) medium to a lighter (less refractive) one, it speeds up and must bend away from the boundary’s normal. This follows Snell’s law: n1 sin θ1 = n2 sin θ2. Because n1 is greater than n2, sin θ2 must be larger than sin θ1, so the refracted angle θ2 is bigger than the incident angle θ1. In other words, the ray appears to bend away from the normal line at the interface. This is why a light ray traveling from water into air, for example, emerges at a wider angle relative to the normal. (Note that if the incident angle is large enough, total internal reflection can occur instead of refraction, but that’s a separate condition.)