Which of the following diagrams best represents the phenomenon of $diffraction$?

• A. A set of parallel wavefronts converging to a single point after passing through a lens.
• B. A set of parallel wavefronts reflecting off a flat barrier at the same angle as incidence.
• C. A set of parallel wavefronts passing through a narrow opening and spreading out in semicircular patterns on the other side.
• D. A set of parallel wavefronts passing through a wide opening and continuing straight with no change in direction.

Answer: (C)

Verified step by step guidance

1. Understand the concept of diffraction: Diffraction is the bending and spreading of waves when they encounter an obstacle or pass through a narrow opening, especially when the size of the opening is comparable to the wavelength of the wave.
2. Analyze each option in terms of wave behavior: - Parallel wavefronts converging after a lens represent refraction and focusing, not diffraction. - Parallel wavefronts reflecting off a flat barrier at the same angle represent reflection. - Parallel wavefronts passing through a wide opening and continuing straight represent minimal or no diffraction because the opening is much larger than the wavelength.
3. Focus on the option describing parallel wavefronts passing through a narrow opening and spreading out in semicircular patterns: This matches the definition of diffraction, where waves spread out after passing through a small aperture.
4. Recall that diffraction causes waves to bend around edges and spread out, creating semicircular or circular wavefronts beyond the opening, which is a key characteristic distinguishing it from reflection or refraction.
5. Conclude that the diagram showing parallel wavefronts passing through a narrow opening and spreading out in semicircular patterns best represents diffraction.