Which phenomenon involves energy crossing a boundary and changing direction due to density differences?

Which phenomenon involves energy crossing a boundary and changing direction due to density differences?

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

Answer: (A)

Refraction is the bending of a wave as it crosses into a medium with a different density (and thus a different propagation speed). When the wave enters the new medium, its speed changes, and because different parts of the wavefront cross the boundary at an angle, the overall path bends. Snell's law describes how the angle changes with the speed difference. A familiar example is light entering water from air, which slows down and bends toward the normal. By contrast, reflection is energy bouncing off the boundary without entering the second medium, diffraction is bending around edges or through openings, and absorption is energy taken up by the material with little or no directional change. So, the phenomenon described is refraction.

Refraction is the bending of a wave as it crosses into a medium with a different density (and thus a different propagation speed). When the wave enters the new medium, its speed changes, and because different parts of the wavefront cross the boundary at an angle, the overall path bends. Snell's law describes how the angle changes with the speed difference. A familiar example is light entering water from air, which slows down and bends toward the normal. By contrast, reflection is energy bouncing off the boundary without entering the second medium, diffraction is bending around edges or through openings, and absorption is energy taken up by the material with little or no directional change. So, the phenomenon described is refraction.