Why is Planck's Constant important?

1 Answer
Jun 6, 2017

Planck's constant is instrumental and an unavoidable constant which appears in quantum mechanics.

Explanation:

Even though it was first introduced in the Planck's law,

uλd(λ)=8πhcλ5dλehcλkT1

Where one quantum of radiation would have an energy, E=hcλ, the concept of quantized radiation was extended by Einstein, later by Bohr in their theories as a part of the old quantum theory.

Today almost all important relationships in quantum mechanics, contain Planck's constant (or the reduced Planck's constant h2π).

Examples would include,

1) de Broglie relation -
λ=hp

2) Schrodinger equation -

ih2πψt=h28π2m()2ψ+V(r,t)ψ

3) Commutator of x and px -

[x,px]=ih2π

And so on.

It is to quantum mechanics, what the constants ε0 and μ0 are to Electricity and Magnetism.