PHYSICS · Single correct · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics
Problem
In a laboratory demonstration, light of wavelength λ passes through two different aperture assemblies that have identical slit spacing d. Assembly X has two slits, whereas Assembly Y has five slits. Students measure that the central maximum produced by Assembly Y is markedly brighter than that produced by Assembly X. Which of the following best explains this observation?
(a) Five slits transmit about five times as much light as two slits, so the central maximum is brighter simply because more photons reach the screen.
(b) The additional slits act like a single aperture of width 5d, and a wider aperture produces a narrower, more intense central diffraction maximum.
(c) Additional slits allow more light to add constructively at the same angles, concentrating approximately the same total energy into a narrower angular region.
(d) Because the intensity of a principal maximum grows only in proportion to the number of slits N, using five slits increases the brightness by roughly 5/2, making the central fringe appear brighter.