Interference Topic

Interference From Two Sources

Concept 3 demos

$Four horizontal rows of green double-slit interference patterns on a dark background, each showing different fringe spacings and diffraction envelopes corresponding to the four slit configurations$

Electroformed Two-Slit Interference

Laser light through precision double slits produces interference patterns that demonstrate the wave nature of light. Four slit configurations allow direct comparison of how slit width and spacing affect fringe …

Green laser passing through Cornell plate mounted on ring stand with finger clamp, producing a horizontal interference pattern on white paper magnetically attached to blackboard

Cornell Plate Double-Slit Interference

A laser illuminates double slits on a Cornell plate, producing an interference pattern on a distant screen. The Cornell plate has multiple slit configurations (varying separation, width, and number of …

$Green laser and PASCO diffraction wheel mounted on optical rail with optical sliders, projecting a faint green interference pattern onto white paper magneted to blackboard$

Variable Double Slit

Demonstrates double-slit interference with variable slit separation using a laser and PASCO diffraction wheel. Students observe the inverse relationship between slit separation and fringe spacing, providing direct verification of.

Gratings

Concept 8 demos

$Green laser on adjustable stand with Cornell diffraction plate, producing a multiple-slit interference pattern on white paper attached to the blackboard; pattern shows a bright central spot with a few side maxima$

Multiple Slit Diffraction

A Cornell plate provides multiple-slit patterns and gratings of various densities. Students observe how increasing the number of slits sharpens the principal maxima while keeping their angular positions fixed, and …

$Projected diffraction pattern in dark room: bright white zeroth-order stripe on left from projector, first-order continuous spectrum (blue through red) on right with discrete blue, green, and red laser spots visible within it$

Lasers and White Light

Compares diffraction of three individual laser wavelengths (red, green, blue) with white light from a slide projector through the same grating. Students see discrete laser spots at specific angles alongside …

$Three PASCO Scientific transmission diffraction gratings in metal slide mounts, labeled 100 LINES/MM, 300 LINES/MM, and 600 LINES/MM, on a green surface$

Transmission Gratings

Demonstrates how grating line density affects angular separation of diffraction orders. Comparing 100, 300, and 600 lines/mm gratings with a laser, students directly observe that higher line density (smaller) produces …

Thin Films

Concept 4 demos

Newton's rings apparatus viewed through the lens, showing small concentric colored interference fringes in the upper-right area of the circular field

Newton's Rings

Projects circular interference fringes formed by the air wedge between a plano-convex lens and a flat glass plate. Students observe that the central spot is dark (due to the phase …

Projected soap film showing colorful interference bands of magenta, green, cyan, yellow, and blue swirling across the film against a dark background

Interference in a Soap Film

Students observe thin film interference as colored bands form in a soap film and evolve over time. The projected image shows how constructive and destructive interference between reflections from the …

Four views of a spinning soap film in a black cup under white light, showing evolution from small concentric rainbow rings at center, to expanded blue central region, to blue-purple field, to large gold and magenta interference pattern

Spinning Soap Film

Demonstrates thin-film interference in a rotating soap film. Centrifugal force creates a parabolic thickness profile, producing concentric colored rings that evolve as the film thins. Students observe the connection between …

Interferometers

Concept 2 demos

Overhead view of interferometer model on green lecture bench, with green ribbons extending from translucent light box on ring stand, routed around bench clamps representing mirrors, with springs providing tension

Interferometer Model

A mechanical model of a Michelson interferometer uses colored ribbons to represent light paths. Sliding one "mirror" (bench clamp) changes the ribbon alignment, showing constructive interference when colored squares match …

Pasco Precision Interferometer on optical rail with green laser on left, interferometer body in center, and circular green interference pattern projected on the wall

Interferometer

A Michelson interferometer splits a laser beam into two paths and recombines them, producing visible interference fringes that shift as the path length changes. Students see direct evidence that light …