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Quantum Physics with a Solo Cup

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

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How it works

What this project is testing.

Planck constant is the bridge between color and energy. Different LED colors emit different photon energies, and those colors can be estimated with a simple diffraction setup.

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This project uses LED turn-on voltage and measured wavelength to get a rough value for h. It is wonderfully scrappy: a cup, a grating, and a graph turning household-scale measurements into quantum physics.

E = h f = \frac{h c}{λ}

Photon energy increases with frequency and decreases with wavelength.

e V \approx \frac{h c}{λ}

The LED threshold voltage gives a rough estimate of the photon energy.

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.

Auto Ranging Digital Multimeter TRMS 6000 with Battery Alligator Clips Test Leads AC/DC Voltage/Account,Voltage Alert, Amp/Ohm/Volt Multi Tester/Diode

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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

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

SUNYIMA 10pcs Mini Monocrystalline Solar Cells Solar System Kit 50mm X 50mm/1.96" X 1.96" 2V 160MA for DIY Charge Solar Panels

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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

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Preferred Apple laptop option for coding, editing, and project-control work.

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$Diffraction Grating sheet 13,500 lines/inch - Double Axis 5ft Long x 6 inches Wide$

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Confirm line density for the measurement. Review requirements and safety guidance before buying.

Digital Caliper Measuring Tool, Stainless Steel Vernier Caliper Digital, Micrometer Calipers with Large LCD Screen, Auto-Off Feature, Inch Millimeter Conversion, 6 Inch Caliper Tools for DIY/Household

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3M Scotch Vinyl Electrical Tape Super 88, 3/4 in x 44 ft, Black, 1 roll, Premium Grade, Rubber Resin Adhesive, PVC Backing, A

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Hefty Party On Disposable Plastic Party Cups, 50 Count, 18 Oz Red Cups for Parties, Tailgates, Birthdays, Holidays, and More, Contoured Shape for Easy Gripping, Strong and Durable

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Project files

Prints, kits, and downloads.

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

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