Planck Diode

7/30/2019 Planck Diode

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BY Rohit sharma


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Plancks Constant1900, Max Planck proposed discrete behavior for an

object of subatomic dimensions - Plancks constant h -the natural unit of action

6.626 x 10-34 J-s, or kgm2/s

It also represents angular momentum.

1905, Einstein stated that electromagnetic radiation islocalized in photons with frequency f and energy: E =hf

1913, Niels Bohr extended idea to electron existingbetween states of discrete energy. Transitions areaccompanied by absorption or emission of photons

with f = E/h.


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The Photoelectric Effect

1902 it was proven that the KEmax of an electron isindependent of intensity of light ray and dependent onthe frequency f.

1905, Einstein formed a fundamental theory where light

is composed of photons = energy quanta.Electrons are ejected (with great velocity from the atom)

by the E of the photon.

Each light quantum consists of an amount of E = hf


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Light Emitting DiodesLight Emitting Diodes have p-n junctions where voltage

yields a flow of current. The carriers (electrons andholes) are injected across the junction producing light.


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Procedure

We first build the device, approximatelytaking 15 minutes. The device consists of 5different colored LEDs, a 6 volt battery

pack, a potentiometer, an on/off switch, a330W resistor, a loose set of black and redwire, and a wire with an alligator clip.

The apparatus is turned on.

The alligator clip is attached to a LED lead.


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Procedure (contd)

The loose wires (black and red) are connected to aMultimeter (which reads the voltage across the LED).

Turning the room lights off, we vary the voltage (withthe potentiometer) to see the max voltage before

shutoff of the LED.We record the value.

After, we turn the potentiometer back to maximum,and we measure the wavelength of each diode with a

spectrometer.


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Apparatus


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Circuit Diagram


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Blue Diode


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Green Diode


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Orange Diode


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Large Red Diode


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Small Red Diode


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Data

Diode Voltage (V) Wavelenghts (

Blue 2.196 640

Green 1.536 695Orange 1.507 695

Large Red 1.530 700

Small Red 1.287 680


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Experimental Results

From before E = hf, therefore, we used the formulah = (e Vl) /c

= 5.84 x 10-34

h = (5.84 + s) x 10

-34

s = [ (1/n)Sin (hi h)

2]-1

s = 1.05


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ConclusionBeing that the s was 1.05, it is evident that the errors in

the experiment were random rather than systematic.This goes to show that this experiment is very effective

and efficient, while at the same time being verysimplistic.

These conclusions therefore exhibit the perfectcharacteristics for an entry level physics course whilemaking it an interesting and EASY method for obtainingone of natures constants.


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Questions?

Planck Diode

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