Which of the following best describes the phenomenon of $diffraction$?

• A. A $wave$ changes direction as it passes from one medium to another due to a change in $speed$.
• B. A $wave$ bends around the edges of an obstacle or aperture and spreads into the region beyond.
• C. A $wave$ bounces off a surface and returns to the original medium.
• D. Two $waves$ combine to form a resultant $wave$ of greater, lower, or the same $amplitude$.

Answer: (B)

Verified step by step guidance

1. Understand that diffraction is a wave phenomenon related to how waves behave when they encounter obstacles or openings.
2. Recall that when a wave passes through a narrow aperture or around the edge of an obstacle, it does not simply continue in a straight line but instead spreads out into the region beyond the obstacle.
3. Recognize that this spreading or bending of waves around edges is what defines diffraction, distinguishing it from other wave behaviors like refraction (bending due to speed change) or reflection (bouncing back).
4. Note that diffraction is most noticeable when the size of the obstacle or aperture is comparable to the wavelength of the wave.
5. Therefore, the best description of diffraction is: 'A wave bends around the edges of an obstacle or aperture and spreads into the region beyond.'