**Planck's constant** was first discovered by Max Planck in experiments that helped lead to the formation of quantum mechanics.^{[1]} He formed the Planck Hypothesis, stating that radiation could only come in discrete packets now called photons. Planck's constant is usually written as *h,* but it's often useful to divide Planck's constant by [math]2\pi[/math], and then it is written [math]\hbar[/math], which is called h-bar:

- [math]\hbar = \frac{h}{2 \pi}.[/math]
^{[2]}

The value of the Planck constant^{[3]} is:

The value^{[4]} of [math]\hbar[/math]:

- [math]\hbar = {{h}\over{2\pi}} = 1.054\ 571\ 726(47)\times 10^{-34}[/math] J·s [math]= 6.582\ 119\ 28(15)\times 10^{-16}[/math]eV·s.

To learn more about Planck's constant please see hyperphysics.

- ↑ Rod Nave Hyperphysics (2015, June 20).
*Plank hypothesis*. [Online]. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/mod2.html#c3 - ↑ Rod Nave Hyperphysics (2015, June 20).
*Plank constant*. [Online]. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/tables/funcon.html - ↑ NIST (2015, June 20).
*Plank constant*. [Online]. Available: http://physics.nist.gov/cgi-bin/cuu/Value?h%7Csearch_for=planck - ↑ NIST (2015, June 20).
*Plank constant over [math]2\pi[/math]*. [Online]. Available: http://physics.nist.gov/cgi-bin/cuu/Value?hbar%7Csearch_for=h-bar

Bethel Afework, Allison Campbell, Jordan Hanania, Kailyn Stenhouse, Jason Donev