Finding the Value of Planck's Constant - A Level Physics PRACTICAL

This video explains an A Level Physics Practical: finding the value of Planck's constant with LEDs.

How to conduct an experiment to find the value of Planck's constant using an LED, a voltmeter and a variable power supply. Planck's constant, h, is the constant of proportionality between the particle-like properties and the frequency of the associated wave.

Thanks for watching,

Lewis

This video is recommended for anyone studying A Level Physics in the following exam boards:
AQA
CIE
Edexcel
Edexcel IAL
Eduqas
IB
OCR A
OCR B
WJEC

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[mariahancock]

These explain the method very clearly, but it would be great to include some sources of error / limitations for each experiment, which would explain why our experimental value is never the same as the standard value.

[charlesbarbour]

I find it strange that you go to the bother of making such a helpful video and some of the comments ask you to provide more information. WTF?!
Thanks for taking the time to do this. It was extremely useful for me.

[isabellesecord]

Thank you so much! This really helped me understand my required practical on Planck's Constant.

[manassehnixon]

You sir are a legend, saving me from failing my as level physics exam! Thank you so much

[master]

You make it so easy to understand! Thank you so much sir! :)

[glennghose]

Its a really good experiment. I like the open circuit board where you can see all the components. Makes it less "black box" physics. Where did you buy the circuit board?

[minxythemerciless]

The apparatus is not well explained. Each LED in the kit has its own dropper resistor. They aren't in parallel. If they were'nt separately fed and all the LEDs were in parallel, the red LED would clamp the voltage and the other LEDs would never light.

[lesnerchai]

I have another suggestion here. We can directly plot the graph of energy(E=eV) vs frequency, so the gradient of the graph will be equal Planck constant, h.

[lesnerchai]

Thank you sir for making this video. Now I know that we can use double slit experiment to find the frequency of light.

[laboratoryoperationsmanage]

Hi @Physics Online! Where did you find/buy that circuit board? I manage a University lab and I think we could use this to improve our current physics lab on Planck's constant!

[Anarchhh]

By multiplying the gradient by the charge on the electron, do you just mean 1.6 x 10^-19?

[Fabian-oclc]

Would you get the same results if the lab where you do the experiment would be located on the ISS? What if the lab is located on the Moon or on Mars?

[xVbM]

What sort of graph would you get if you plotted the voltage to the wavelength instead of the reciprocal wavelength? Also is there a way of calculating planks constant without doing 1/wavelength and just doing wavelength?

[siddharthdahiya]

Are there any research papers for this?

[forest]

Is this needed for A Level Edexcel Physics? Thanks!

[ShawnGradybooks]

Brilliant. Thank you. Simply stated and answered the question I had that several documentaries didn’t answer.

[pierreretief]

I do have a question. If you know you will get a straight line, why not only do the test with the highest voltage LED, that should give you a V and lambda and you can use his last blue formula, what is the point of finding the gradient?

[troyfrei]

HOLD ON. Now they make LEDs that turn on at a lower voltage. If you video is true how does LEDs turn on at a lower voltage? Now a days TV are made for LED and other stuff and the turn on voltage is lower each year, so is Plank con wrong? Or does Plank con just gets smaller each year? Please help me to understand.

[past]

The only problem here is that the wavelength of the LED's, as given in the datasheets are calculated from planks constant. You are using circular logic!

[aarzoomir]

what exam board and spec are these videos built around?