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Optics

World's Smallest Ruler to Measure Light

Start with the video, then use the science notes and recommended parts below to follow the idea behind the build.

Optics

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How it works

What this project is testing.

Light waves are too small for an ordinary ruler, so this project uses interference as the ruler. A Michelson interferometer splits one laser beam into two paths and recombines them into bright and dark fringes.

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By nudging one mirror with a micrometer and counting fringe shifts, the setup turns nanometer-scale distance changes into something visible. Each shift is the light reporting that the path length changed.

2Δ x = N λ

Moving a mirror by a distance changes the round-trip path by twice that distance, producing N fringe shifts.

λ = \frac{2Δ x}{N}

Count the fringes and the mirror motion gives the laser wavelength.

Recommended parts

Products used in this project.

Affiliate links may earn Keystone Science a commission. Match ratings, values, sizes, polarity, and safety requirements to your own build before buying.

WOWOONE Laser Diode 30Pcs 5V 650nm 5mW Mini Red Dot Laser Head, 6mm Outer Diameter Laser Module with Leads, for Arduino Laser DIY Electronics Projects, High-Stability Red Laser Diode

laser / laser pointeroptics

30pcs 5V 650nm 5mW Mini Red Dot Laser Diode Modules with Leads

$12.994.6(152)

Laser safety matters. Keep recommendations to low-power modules and add eye-safety warnings. Review requirements and safety guidance before buying.

RUEHALF Front Surface Mirrors, 100 * 100 * 3mm First 1st Surface Mirror,Surface Mirror Optics Quality for Engineering and Scientific Project

mirroroptics

Front Surface Mirror, 100 x 100 x 3mm, First Surface Optics Quality Mirror

$19.04

For interferometer/optics use, prefer first-surface mirrors over bathroom/craft mirrors. Amazon review evidence is sparse. Review requirements and safety guidance before buying.

Optical Glass Cube Dichroic Beam Splitter Prism Ratio 50:50 Spectrome Sicence 15X15X15MM

beam splitteroptics

Optical Glass Cube Dichroic Beam Splitter Prism, 50:50, 15x15x15mm

$13.994.8(17)

Specialty optics have fewer Amazon reviews; verify size and wavelength before publishing. Review requirements and safety guidance before buying.

$Physics Optical Experiment Set Multifunction Reflector Refraction Triangular Prism Convex Lens Concave Mirror Dial Linear Light Source Teaching Demonstration Equipment for Teacher Student Education$

lensoptics

Physics Optical Experiment Set with Prism, Convex Lens, Concave Mirror, and Linear Light Source

$18.994.3(198)

Specialty optics may need size and focal-length review before publishing.

Ackers High Borosilicate Glass Measuring Cup Set with Pour Spout,60ml(2OZ),120ml(4OZ), 250ml(8OZ) Glass Measuring Beaker for Kitchen or Restaurant, Easy to Read

glassfabrication

Ackers High Borosilicate Glass Measuring Beaker Set with Pour Spout

4.5(3,500)

5PCS 3.3V-5V Photodiode Module LM393 Light Sensor Switch Module for Arduino Raspberry Pi Photosensitive Diode Detection Switch

photodetector / photodiodesensor

5PCS 3.3V-5V Photodiode Module LM393 Light Sensor Switch Module

$7.995.0(4)

Good functional match for a photodiode module, but it has sparse Amazon review evidence. Review requirements and safety guidance before buying.

Logitech HD Pro Webcam C920, Widescreen Video Calling and Recording, 1080p Camera, Desktop or Laptop Webcam

camerarecording/measurement

Logitech HD Pro Webcam C920, 1080p Widescreen Video Calling and Recording

$68.474.6(33K)

Kynup Digital Caliper, Caliper Measuring Tool with LCD Screen, Electronic Micrometer Caliper with Auto-Off Feature, Inch and Millimeter Conversion(0-6")

micrometermeasurement

Kynup Digital Caliper, Caliper Measuring Tool with LCD Screen, Electronic Micrometer Caliper with Auto-Off Feature, Inch and Millimeter Conversion(0-6")

$9.994.6(12K)

Project files

Prints, kits, and downloads.

Diagrams, printable files, kits, or companion downloads will appear here when they are ready to use.

Coming soon

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