Which term describes incidence when the beam strikes the boundary at 90 degrees?

Which term describes incidence when the beam strikes the boundary at 90 degrees?

• A. Normal incidence
• B. Oblique incidence
• C. Lateral incidence
• D. Head-on incidence

Answer: (A)

Normal incidence describes a beam hitting the boundary perpendicularly. The angle of incidence is measured from the boundary’s normal, so a 0° angle to the normal means the beam is perpendicular to the surface. In this case, the reflection goes straight back along the incoming path and any transmitted wave passes through without bending. Oblique incidence refers to any non-perpendicular angle, where reflection and refraction occur at angles relative to the normal.

Normal incidence describes a beam hitting the boundary perpendicularly. The angle of incidence is measured from the boundary’s normal, so a 0° angle to the normal means the beam is perpendicular to the surface. In this case, the reflection goes straight back along the incoming path and any transmitted wave passes through without bending. Oblique incidence refers to any non-perpendicular angle, where reflection and refraction occur at angles relative to the normal.