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Anti-Reflection Coating
Katharine B. Blodgett · Public domain (expired patent)
Charlie

Creato da

Charlie

22. settembre 2026DE
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Anti-Reflection Coating

Katharine Blodgett at General Electric, working with Irving Langmuir, learned to build soap-like films one molecule-thick layer at a time. Stacking just enough layers onto glass, she made it nearly invisible: light reflected from the top of the film and from the glass beneath cancelled out. **US 2,220,861**, "Reduction of surface reflection", Blodgett, assigned to General Electric, filed 16. June 1938, granted 5. November 1940: a coating whose "optical thickness … corresponds at least approximately to a quarter wave length of visible light" and whose refractive index is "intermediate" between air and the glass. **You measure the reflection a coating removes**, design one in a notebook, and watch quarter-wave interference happen in a soap film.
Principiante
90 minutes

Istruzioni

1

Measure bare glass

Clip the solar cell to the multimeter (DC mA). In a dim room shine the laser straight onto the cell and note the current. Then bounce the beam off a clean microscope slide, close to perpendicular, onto the cell. Note that current. Never look along the beam.

Materiali per questo passaggio:

Vetrini da microscopio con coprioggettoVetrini da microscopio con coprioggetto1 confezione
Solar Cell Mini - 350mVSolar Cell Mini - 350mV1 pezzo

Strumenti necessari:

Puntatore laserPuntatore laser
MultimetroMultimetro
Alligator to Alligator CablesAlligator to Alligator Cables
2

Mix a film solution

Stir 1 part detergent and 1 part glycerin into 10 parts water in a jar. Bend copper wire into a 60 mm loop with a handle.

Materiali per questo passaggio:

Detergente delicatoDetergente delicato20 ml
Glicerina (vegetale)Glicerina (vegetale)20 ml
Filo di rameFilo di rame1 metro

Strumenti necessari:

Barattolo di vetroBarattolo di vetro
Set di pinzeSet di pinze
3

Watch a film thin

Dip the loop and hold it upright in front of black card, lit by a window behind you. Colour bands slide down as the film drains; at the top a black band appears - a film too thin to reflect.

Materiali per questo passaggio:

Cartoncino neroCartoncino nero1 foglio
4

Fresnel, coating design, soap film

Caricamento del notebook Jupyter…
5

History & Context

**What the patent specifies:** a surface layer of quarter-wave optical thickness with a refractive index between those of the surrounding medium and the glass. **Modern build (derived):** measurement and design only - production coatings are evaporated in vacuum. Blodgett's stearate films were too soft to wipe clean. Alexander Smakula at Zeiss had developed coatings evaporated in vacuum in 1935; that durable route won, and today almost every camera lens and eyeglass is coated, often with many layers. Their limits: a single layer is perfect at only one wavelength, and coatings scratch.
Passo 5 - Image 1

Materiali

6

Strumenti richiesti

5
Totale stimato
Ciò che il maker ha acquistato. I materiali senza prezzo si trovano dove li compri tu.
€1.93

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