Which phenomenon occurs when light returns into the same medium after striking a boundary, without crossing into the second medium?

Which phenomenon occurs when light returns into the same medium after striking a boundary, without crossing into the second medium?

• A. Refraction
• B. Diffraction
• C. Interference
• D. Reflection

Answer: (D)

Reflection is the phenomenon described. When light hits a boundary and stays in the original medium, it bounces back instead of crossing into the second medium. On a smooth boundary, the angle at which the incoming light hits the boundary (the angle of incidence) equals the angle at which it leaves (the angle of reflection). This keeps the light in the same medium, which you see in everyday examples like seeing your face in a mirror or a calm lake surface. By contrast, refraction happens when light crosses into the second medium and changes speed and direction, diffraction is light bending around edges or through small openings, and interference is the combination of multiple waves that can amplify or cancel each other.

Reflection is the phenomenon described. When light hits a boundary and stays in the original medium, it bounces back instead of crossing into the second medium. On a smooth boundary, the angle at which the incoming light hits the boundary (the angle of incidence) equals the angle at which it leaves (the angle of reflection). This keeps the light in the same medium, which you see in everyday examples like seeing your face in a mirror or a calm lake surface.

By contrast, refraction happens when light crosses into the second medium and changes speed and direction, diffraction is light bending around edges or through small openings, and interference is the combination of multiple waves that can amplify or cancel each other.