The bending of a wave caused by a change in speed as it moves from one medium to another is termed?

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

Answer: (D)

When a wave crosses a boundary and its speed changes, the path bends. This happens because different parts of the wavefront slow down or speed up at different rates once they’re in the new medium, so the direction shifts. That bending is refraction. The frequency stays the same across the boundary, but the wavelength adjusts to the new speed in the second medium. For light, entering a slower medium makes the ray bend toward the normal; entering a faster medium makes it bend away from the normal. Other terms describe different effects: dispersion involves different wavelengths bending differently and separating, diffraction is bending around edges or through openings, and reflection is the wave bouncing off the boundary.