Electroformed Two-Slit Interference - Physics Demonstrations - Electroformed Two-Slit Interference | Physics Undergraduate Labs

This demonstration uses a Class 3A/3R green laser (5 mW). Never look directly into the beam or allow specular reflections toward students. The polished steel plate is covered with a reflection shield specifically to prevent stray reflections. Ensure the laser beam terminates on the projection screen or a diffuse surface, never allowing it to exit the demonstration area toward students.

Purpose

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 spacing and the diffraction envelope.

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

Electroformed double-slit slide in a black 35mm-style frame with a specifications label listing four patterns: A (0.04 mm width, 0.250 mm spacing), B (0.04 mm, 0.500 mm), C (0.08 mm, 0.250 mm), D (0.08 mm, 0.500 mm)

Optical bench with DPSS green laser (black box, left), slit slide in adjustable carriage (center), and construction-paper reflection shield over polished steel plate (right)

Figure 1: Interference patterns from the four double-slit configurations (A–D), projected on a screen. Differences in fringe spacing and diffraction envelope width are clearly visible.

Figure 2: Electroformed double-slit slide with four configurations: slit widths of 0.04 and 0.08 mm, slit spacings of 0.25 and 0.5 mm.

Figure 3: Complete apparatus: DPSS green laser, slit slide in horizontally-adjustable carriage, and construction-paper reflection shield on the optical bench.

Optical Slider

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Polished Steel Plate

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Horizontally Adjustable Optical Slider

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2 in 4 Slot Slide Holder

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Safety Warnings

Warning: Laser Safety

Purpose