Measuring the Planck's constant with Arduino
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With this shield produced by Steplb it's easy to study the Planck's constant using a normal Arduino Board. The method is based on studying the led threshold voltage. We provide 4 different leds with given wavelength.
This shield makes the experiment repeatable and prevents students from damaging the components. The shield comes with a user manual. Using the Arduino board allows you to make measurements with a computer.
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What will you Learn
- Measurement
- Linear regression
- Basics of quantum physics
- LED diode basics
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Content
- User manual
- Sketch to load in your board ( open, you can modifiy )
- Planck's Shield
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Theory of operation
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Light-emitting diodes (LEDs) convert electrical energy into light energy. They emit radiation (photons) of visible wavelengths when they are forward biased. This is caused by electrons from the `N' region in the LED giving up light as they fall into holes in the `P' region. The graph above shows the current-voltage curve (IV curve) for a typical LED. The 'turn-on' voltage Ut is about the same as the energy lost by an electron as it falls from the N to the P region. In this experiment you will find the point at which the light `goes on' by gradually adjusting the voltage.
The energy produced by photons (hc/λ), is assumed to be equal to that lost by each electron, qV: where q is the charge on an electron (q = e = 1.6 x 10^-19 C), U is the turn-on voltage, λ is the wavelength of light emitted in metres, and c is speed of light c = 3.0 X10^8 m/s.
Above you can also see calculation for the measurement error. LED manufacturers state the wavelength of the LEDs with the precision about Δλ = 20nm - 30nm and the precision of my voltmeter is ΔU = 0.01V.
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