Planck's constant

[Daymare17]

Can anyone explain in layman's terms what the Planck's constant is? I'm not an utter novice on quantum physics but the wikipedia article on Planck's is way too professional for me.

[JaKiri]

Basically, it describes the base multiple for work (ie, energy interactions) to happen in. It's used for various things, including calculating the energy of photons.

[Martin]

Can anyone explain in layman's terms what the Planck's constant is? I'm not an utter novice on quantum physics but the wikipedia article on Planck's is way too professional for me.

 

the easiest access to it is by visualizing the photoelectric effect

 

this is a simple vacuum tube experiment already done in the 1890s

and it was realized already in 1905 that it means that

 

LIGHT MUST ARRIVE IN LITTLE BUNDLES ("photons") whose energy is proportional to their frequency

 

planck's h is the proportion

 

it is the ratio of frequency to energy----of any photon in the universe

 

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planck's h is the proportion followed by a lot of other things and it gets into a huge amount of stuff, like quantizing the spin of stuff and like atoms etc etc----but that is not the easiest mental doorway to go thru

 

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the easiest doorway is to say "look, the universe is full of light and all this light is in a certain sense granular-------and for each and every grain of light in the whole universe, the amount of energy the thing can deliver (to tickle your retina cell in your eye, or give you a suntan, or excite a photoelectric cell, or cause chemical change in a green leaf, or cancer, or whatever) the amount of energy the thing carries is

always proportional by a fixed proportion h to the frequency that that particular grain of light is wiggling or buzzing or whatever, vibrating."

 

vibrancy is proportional to energy, in grains of light, everywhere throughout the universe, by the same proportion h, called plancks constant.

 

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this has to be an incredibly impressive proportionality built into the universe, or else an incredibly weird coincidence.

 

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so you have to start by picturing this 1890s glass ball with a vacuum in it, and two metal plates, and you shine a light of some color on one of the plates (or maybe it is UV light so it doesnt have a visible color, but it has some wavelength and some frequency)

 

and you find that it causes electricity to jump between the plates.

you have to really think about this experiment and what was observed

 

in 1890s they observed that the voltage of the jump does not depend on how bright the light----tho the amount of current does---the voltage barrier it can jump depends on the frequency of the light

 

I have to go now,

maybe someone else will finish explaining

[CPL.Luke]

an easy way of thinking about it is

 

E=hf

energy=(plancks constant)(frequency)

 

in my science class we calculated plancks constant using led's a multimeter and a spectrometer

 

we graphed our results as energy vs. frequency in a scatter plot. In this scatter plot the slope of the line of best fit is plancks constant

[swansont]

Planck's constant is also the unit of angular momentum, so it tells you the minimum change there can be in a system's tendence to rotate (or in some other way behave like it is doing some kind of circular motion)

[Martin]

Can anyone explain in layman's terms what the Planck's constant is?....

 

OK I'm back, and I see several others have contributed to the answer. It is a big topic, what h is.

 

I was talking about the photon energy facet-----the E = hf----

where if you want to know the energy of an individual bundle of light energy, a photon, then you just take the frequency of that bundle of light and multiply by h.

 

You should know the actual size of h.

that requires using UNITS. for example an electronvolt is an amount of energy. it is enough to kick an electron across a gap against a one volt barrier. many chemical reactions require that much energy, or release that much, at the atomic level, when they happen.

 

as a unit of frequency try a "Terahertz"-----ONE TRILLION CYCLES PER SECOND. Standard metric abbreviation is THz.

 

1 THz = 10¹²

 

PLANCK'S CONSTANT IS 0.0004 ELECTRONVOLTS PER TERAHERTZ.

 

it is the universal proportion of a bundle's energy to its frequency.

so if you have a photon of light (imagine a wavepacket blip) and the predominant frequency in it is 1000 THz

then that wavepacket blip of light carries a punch of 4 eevee.

 

Most sunlight, including visible light, has a frequency of only a few hundred THz. Like 500 Terahertz. so it is not going to give some molecule a punch like 4 eevee, but more mild, like 2 eevee

 

but you should remember some definite value for h

and lacking a better it can be

0.0004 eevee per Terahertz

[Jordan14]

I think everyone has done an inpressive job of decribing what planck's constant is.,, and I won't add to this.

 

But if you are getting into Quantum Physics, and haven't already read the following books I say that you should, and stay apart of SFN than you will learn Quantum even easier:

 

Search for Shrodinger's cat - John Gribbin, what I think is the perfect start for any quantum physicist, I think that Gribbin is a genius in the sense of how he portrays Quantum's coplexity in simple terms

 

Shrodinger's Kittens - the sequel

 

A brief history of time - Stephen Hawking, not purely about the Quantum world but both quantum, cosomology, relitivity just a fantastic read again all the explanations are layed in easy to understand terms

 

Also a search on the internet will provide valuable resources:

 

A quick search and I found:

 

http://theory.uwinnipeg.ca/mod_tech/node143.html

 

I hope this all helps .

 

Enjoy

[JaKiri]

The Elegant Universe is better, much better, than A Brief History of Time.

[Jordan14]

Actually I haven't read that always wanted to get around to it but never did.