# "how to calculate Planck const at home"

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Hello everyone I am new here

I would like to know how to calculate the h constant at home...

It is hard to understand, base log 10 systems..

It is this base log system of 10, that is really hindering me to move forward.

It is also Newtonian Mechanics, that is " confusing me " with photon energy and light "speeds"..

Then you have the fractions to deal with.

However, Distance and Frequencies is my main focus...

Until I know this I refuse to move forward with anything else..

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So what you're saying is you don't know how to use scientific notation or decimal points?

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So what you're saying is you don't know how to use scientific notation or decimal points?

Yes.., I confuse all the zeros and the dot....... I assume that to be the 10ths place, but then I hear its called the radix dot, in floating point variables in round off errors...

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Planck originally calculated the value of the constant from an analysis of the "black body" spectrum. But this is pretty complicated - especially if you are not even comfortable with fractions and basic algebra.

Maybe you should start here: https://www.khanacademy.org/math/pre-algebra

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Imagine simple electronic circuit, battery with red LED (Light Emitting Diode).

Single red photon which has 650 nm wavelength has energy E=h*c/650nm = 3.056*10^-019 J

3.056*10^-19 J / 1.602*10^-19 = 1.9 eV (in electron volt unit)

Electron in electronic circuit that has voltage U has kinetic energy E=e*U

so if voltage in above circuit will be smaller than 1.9 V, there will be too little energy to emit red photon, and LED won't shine.

Q=I*t,

current I you read from ampere meter,

time t you read from stopper,

so quantity of electrons in electronic circuit is:

quantity of electrons = Q/e = I*t/e

(for t=1 s, current I=1 A, it's 6.24*10^18 electrons per second)

Electron is emitting red photon, and losing its kinetic energy ("voltage drop on element").

Typical LED allows 10-35 mA so it's 0.01-0.035 * 1s / 1.602e-19 = 6.242e+16 to 2.185e+17 electrons per second passing through it.

(After exceeding limit I, LED will burn - too many electrons/photons per second will destroy it (if you will touch it, you can feel how hot it's becoming very quickly) )

If you will repeat this experiment with green LED, blue LED, UV LED, white LED you will see different threshold voltages at which they emit light.

UV LED and white LED are similar, because in reality white LED is emitting UV photon that is later absorbed by fluorescent material and emitted in full visible spectrum.

UV LED is not working with 2 AA 1.25 V (2.5 V total) batteries, but it's working with 3 AA (3.75 V).

UV photon with 350 nm, needs U > 3.54 V.

UV photon with 400 nm, needs U > 3.1 V.

Experimentally checked.

Do you now see how to calculate h?

Edited by Sensei
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Imagine simple electronic circuit, battery with red LED (Light Emitting Diode).

Single red photon which has 650 nm wavelength has energy E=h*c/650nm = 3.056*10^-019 J

3.056*10^-19 J / 1.602*10^-19 = 1.9 eV (in electron volt unit)

Electron in electronic circuit that has voltage U has kinetic energy E=e*U

so if voltage in above circuit will be smaller than 1.9 V, there will be too little energy to emit red photon, and LED won't shine.

Q=I*t,

current I you read from ampere meter,

time t you read from stopper,

so quantity of electrons in electronic circuit is:

quantity of electrons = Q/e = I*t/e

(for t=1 s, current I=1 A, it's 6.24*10^18 electrons per second)

Electron is emitting red photon, and losing its kinetic energy ("voltage drop on element").

Typical LED allows 10-35 mA so it's 0.01-0.035 * 1s / 1.602e-19 = 6.242e+16 to 2.185e+17 electrons per second passing through it.

(After exceeding limit I, LED will burn - too many electrons/photons per second will destroy it (if you will touch it, you can feel how hot it's becoming very quickly) )

If you will repeat this experiment with green LED, blue LED, UV LED, white LED you will see different threshold voltages at which they emit light.

UV LED and white LED are similar, because in reality white LED is emitting UV photon that is later absorbed by fluorescent material and emitted in full visible spectrum.

UV LED is not working with 2 AA 1.25 V (2.5 V total) batteries, but it's working with 3 AA (3.75 V).

UV photon with 350 nm, needs U > 3.54 V.

UV photon with 400 nm, needs U > 3.1 V.

Experimentally checked.

Do you now see how to calculate h?

Seems like I need some materials I will practice the " math formula here" and practice till I get it right, and pay " more attention" to them exponent more than anything else..Since you have typed in the answers to the math here above, it will make life easier thanks! I make it habit to do things 1000 times over till I get it right, no joking either.

You say:

in reality white LED is emitting UV photon that is later absorbed by fluorescent material and emitted in full visible spectrum."

If you may can you explain this a little more, it has me very interested...

full visible spectrum? you mean colors right?

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What am I doing wrong with this calculation>>>???

Is it the calculator???

E=h*c/650nm = 3.056*10^-019 J
6.626^-33*299.792458 = 2.37423368261187e-25<------------------thats the way it comes out of the "online" calculator
2.37423368261187e-25/650nm = 3.65266720401826e-28<------------------thats the way it comes out of the "online" calculator

So what you're saying is you don't know how to use scientific notation or decimal points?

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Is it the calculator???

Perhaps. These values are very small, and some broken calculators might be doing calcs wrong..

E=h*c/650nm = 3.056*10^-019 J

6.626^-33*299.792458 = 2.37423368261187e-25<------------------thats the way it comes out of the "online" calculator

2.37423368261187e-25/650nm = 3.65266720401826e-28<------------------thats the way it comes out of the "online" calculator

No..

You are using wrong constant values.

These results are also incorrect.

Enter correct constants to OpenOffice Spread Sheet and you will get this:

h * c = 6.62607e-34 * 299792458 = 1.9864e-25

1.9864e-25 / 650e-9 = 3.056e-19

Edited by Sensei
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If you want to save some time you can type calculations into the Google search bar as well.

It can also convert many constants into their numerical values.

ie. Planck Constant * speed of light = h*c =

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If you want to save some time you can type calculations into the Google search bar as well.

It can also convert many constants into their numerical values.

ie. Planck Constant * speed of light = h*c =

Right. But you have to remember that e is Euler number, not e elementary charge.

So in our case it's (what we were talking about in #5 post):

Edited by Sensei
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Right. But you have to remember that e is Euler number, not e elementary charge.

So in our case it's (what we were talking about in #5 post):

Yeah, garbage in, garbage out still applies.

Mostly just beneficial in terms of speed and allowing Google parse your meaning for you.

Can do: "elementary charge * e *1e5=" and Google can correctly parse it.

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Right. But you have to remember that e is Euler number, not e elementary charge.

So in our case it's (what we were talking about in #5 post):

Yeah, garbage in, garbage out still applies.

Mostly just beneficial in terms of speed and allowing Google parse your meaning for you.

Can do: "elementary charge * e *1e5=" and Google can correctly parse it.

I was told that e means exponent..in the other thread, but this explanations makes sense, because this has me very confused, its a shame " other members" don't say anything about this, and let others look bad,

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the use of symbols can change depending on their context of use, there isn't enough letters in the alphabet for every formula to maintain unique symbols for variables and constants. So you will find that e can have many meanings depending on the models being examined. There is some conventional symbols but there is always exceptions.

for example

p=pressure

p=position

is one example of multiple uses for p

symbols are defined according to the model itself, however with all the various models the same symbol can be used in a different context and is defined differently according to that model.

Edited by Mordred
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Yeah, garbage in, garbage out still applies.

Mostly just beneficial in terms of speed and allowing Google parse your meaning for you.

Can do: "elementary charge * e *1e5=" and Google can correctly parse it.

I don't mean to to say this, and sorry but I am observing that there are more than just one way to calculate this, and maybe that is worth wondering about in relation to numbers in general...Too much input here, I wish " someone can decide" which is which...

the use of symbols can change depending on their context of use, there isn't enough letters in the alphabet for every formula to maintain unique symbols for variables and constants. So you will find that e can have many meanings depending on the models being examined. There is some conventional symbols but there is always exceptions.

This does not make sense at all, and it's no help sorry, and it is misleading...

I am now convinced some people here do not know what they are talking out, or either choose to deliberately make others " look and feel dumb"

I am not the only one talking about this by the way trust me when I tell you...

It makes the forum look bad....

Such a simple question and such a complex answer...Somehow I feel someone is laughing at all of us!

You say: There is some conventional symbols but there is always exceptions.

OK, uhmm which ones???

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um no the answer is accurate, e use in mathematics is exponent, but it is also used to mean energy or Eueler number or the charge of an electron. The answer I provided is accurate. To this statement

I was told that e means exponent..in the other thread, but this explanations makes sense, because this has me very confused, its a shame " other members" don't say anything about this, and let others look bad,

You say: There is some conventional symbols but there is always exceptions.

OK, uhmm which ones???

c in physics by convention usually means the speed of light

h is the planck constant

conventional constants are ones that are used so frequently that everyone accepts their meaning in the majority of models. However there is nothing preventing a model from using c to represent a missing value with another meaning

here is a list of some of the conventional ones

http://hyperphysics.phy-astr.gsu.edu/hbase/tables/funcon.html

however as I mentioned there are examples where fundamental constants are used in a different context such as "e"

Edited by Mordred
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p=pressure

p=position

is one example of multiple uses for p

symbols are defined according to the model itself, however with all the various models the same symbol can be used in a different context and is defined differently according to that model.

Where did you see p for position?

p is momentum in physics..

position is x

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oops yeah your right my bad lol, was distracted when I typed that

Edited by Mordred
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um no the answer is accurate, e use in mathematics is exponent, but it is also used to mean energy or Eueler number or the charge of an electron. The answer I provided is accurate. To this statement

c in physics by convention usually means the speed of light

h is the planck constant

conventional constants are ones that are used so frequently that everyone accepts their meaning in the majority of models. However there is nothing preventing a model from using c to represent a missing value with another meaning

here is a list of some of the conventional ones

http://hyperphysics.phy-astr.gsu.edu/hbase/tables/funcon.html

however as I mentioned there are examples where fundamental constants are used in a different context such as "e"

This is a simple home experiment" .

I would prefer to hear this:

There are many ways to calculate the h constant ...

Yes?

No?

Its very simple..

oops yeah your right my bad lol, was distracted when I typed that

Or maybe you simply did not know? "BUT" THANKS FOR BEING HONEST!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 50/50

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e is elementary charge when it is usually used in physics equation.

e inside of value f.e. 1e6 = 1000000 is exponent in Scientific notation..

http://en.wikipedia.org/wiki/Scientific_notation

e (equal to 2.71828....) is Euler number

http://en.wikipedia.org/wiki/E_%28mathematical_constant%29

Used mostly in mathematics.

Three completely unrelated usages of 'e'....

You HAVE TO know which one is used at the moment..

Every scientists know it from context of equation.

Edited by Sensei
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Or maybe you simply did not know? "BUT" THANKS FOR BEING HONEST!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 50/50

anyone can make an honest mistake. No matter how much they know. One shouldn't imply an honest mistake with knowledge or ability. If I thought my first answer was correct I would have provided an answer showing an example, instead of admitting the error.

Edited by Mordred
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There are many ways to calculate the h constant ...

Of course there is many ways to calculate h, or any other physical constant.. That's how we verify whether it's correctly calculated - checking it different method.

In post #5 I gave you a way to measure it and calculate using electronic circuit, with just a couple instruments like voltage meter, ampere meter, stopper, with just a few equations.. h is derived from kinetic energy of electron needed to emit photon with well known energy/wavelength..

Instead of discussion how to make experiment we're again talking about some basic things unrelated to subject..

Edited by Sensei
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Of course there is many ways to calculate h, or any other physical constant..

In post #5 I gave you a way to measure it and calculate using electronic circuit, with just a couple instruments like voltage meter, ampere meter, stopper, with just a few equations.. h is derived from kinetic energy of electron needed to emit photon with well known energy/wavelength..

Instead of discussion how to make experiment we're again talking about some basic things unrelated to subject..

No , no one ever told me " ever" not even online that there are many ways to calculate h.

Can you provide me a link that says you can??

Thanks for telling me though..

I'm not the only one going off topic either, I paused a bit their for others to get the " options" on e out of the way.

As usual I am thankful for your time.

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http://www2.cose.isu.edu/~hackmart/planck%27s.PDF

this one isn't particularly home experiment

http://arxiv.org/abs/1203.0102

http://backreaction.blogspot.ca/2012/05/testing-variations-of-plancks-constant.html

this video will be helpful, particularly in examples of how to do the calculations (he shows a nice easy method of doing the exponent calculations, that will greatly simplify your calculator problems)

http://www.brightstorm.com/science/chemistry/the-atom/plancks-constant/

this video series will help on the exponent rules

Edited by Mordred
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anyone can make an honest mistake. No matter how much they know. One shouldn't imply an honest mistake with knowledge or ability. If I thought my first answer was correct I would have provided an answer showing an example, instead of admitting the error.

Don't mean to ask this, its just a simple observation.

You say: If I thought my first answer was correct I would have provided an answer showing an example.

So then, you must have known the answer to be incorrect in the 1st place?

http://www2.cose.isu.edu/~hackmart/planck%27s.PDF

this one isn't particularly home experiment

http://arxiv.org/abs/1203.0102

http://backreaction.blogspot.ca/2012/05/testing-variations-of-plancks-constant.html

this video will be helpful, particularly in examples of how to do the calculations (he shows a nice easy method of doing the exponent calculations, that will greatly simplify your calculator problems)

http://www.brightstorm.com/science/chemistry/the-atom/plancks-constant/

thanks

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no it simply means I typed position without thinking about it and didn't realize it, wife was yacking at me at the time. (if your married you can understand how distracting that can be lol)

Edited by Mordred

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