Which are the two conditions for refraction?

Which are the two conditions for refraction?

• A. Oblique incidence; Different propagation speeds
• B. Normal incidence; Same propagation speeds
• C. Oblique incidence; Same propagation speeds
• D. Normal incidence; Different propagation speeds

Answer: (A)

Refraction occurs when a wave crosses a boundary into a medium with a different propagation speed and does so at an angle rather than straight on. The change in speed between media causes the wavefront to bend, so the transmitted ray changes direction according to Snell's law. If the incidence is normal, there is no bending even if speeds differ, and if the speeds are the same in both media, there is no bending even with an oblique approach. Therefore, the two conditions for refraction are hitting the boundary at an angle and having different propagation speeds.

Refraction occurs when a wave crosses a boundary into a medium with a different propagation speed and does so at an angle rather than straight on. The change in speed between media causes the wavefront to bend, so the transmitted ray changes direction according to Snell's law. If the incidence is normal, there is no bending even if speeds differ, and if the speeds are the same in both media, there is no bending even with an oblique approach. Therefore, the two conditions for refraction are hitting the boundary at an angle and having different propagation speeds.