### The value of Planck's Constant

Posted:

**Thu Oct 01, 2015 3:51 pm**I don't understand how was the value of Planck's constant derived?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=15&t=5594

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Posted: **Thu Oct 01, 2015 3:51 pm**

I don't understand how was the value of Planck's constant derived?

Posted: **Thu Oct 01, 2015 8:19 pm**

Planck hypothesized that just like how water's smallest unit is a water molecule, energy also works the same way and can be expressed in discrete or "quantized" units. Therefore Planck's constant is used as a proportionality constant that links the particle's frequency of its electromagnetic wave to its total energy (E=hv) in order to come up with these "quantized units".

Posted: **Fri Oct 02, 2015 12:47 am**

Planck's constant was determined empirically as experiments relating frequency to energy reveal the value of this constant. If you were to plot a graph of energy versus frequency in which the y-axis was labeled Energy and the x-axis was labeled frequency you would get a straight line with a slope of 6.626x10^-34, which is Planck' constant.

Posted: **Fri Oct 02, 2015 10:59 am**

Planck's Constant was calculated from experimental data of E=hv. In this equation, the value of energy and frequency is directly proportional to each other. This is the same equation as y=mx where m is the slope. In the same way, the value of Planck's Constant represent the slope of energy vs. frequency graph. Therefore, by experimentally determining values of energy with frequencies (must be two or more of each), value of Planck's constant can be derived from h=(E2-E1)/(v2-v1).