Q.A diffraction pattern is obtained by making blue light incident on a narrow slit. If blue light is replaced by red light, then the diffraction bands _______. (A) disappear
(B) become broader
(C) become narrower
(D) remain same

Diffraction is the bending of light into the geometric-shadow region of an obstacle, becoming noticeable specifically when the obstacle or aperture size is comparable to light's own wavelength; ray optics, which predicts perfectly sharp shadows, cannot explain it. Physically, light does not literally curve around an edge -- per Huygens' principle, points along the obstacle's edge itself act as secondary sources emitting into the shadow region, exactly as any other point on an unobstructed wavefront would. Diffraction is closely related to interference, and can be understood as the interference of very many (not just two) overlapping secondary wavelets from across the whole diffracting aperture. …