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Activity Discussion Science & Technology What is Planck’s constant? Reply To: What is Planck’s constant?

• ### Manpreet

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June 9, 2021 at 9:32 pm
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Planck’s constant was devised by a German physicist – Dr. Max Planck.

Planck’s constant is a fundamental physical constant, used in quantum mechanics (the branch of physics dealing with tiny particles that make up matter and the forces involved in their interactions). It is denoted by the letter – ‘h’. it is a proportionality constant with a value 6.62607015 * 10 (to the power minus 34).

Planck – Einstein relation –

The planck – Einstein relation gives the relation between energy carried by a photon and frequency of its associated electromagnetic wave.

E = h*f (where E = energy, h = planck constant and f = frequency )

The S.I. units of h = J.s (Joule – second)

Thus, due to this mass – energy equivalence, Planck’s constant relates mass to frequency.

During calculations, the value of planck constant (h) can be used as 6.6 * 10 (to the power minus 34)

Values of Planck’s constant –

In S.I. units, h = 6.6260715 * 10<sup>-34 </sup>J.s

In MKS (meter – kilogram – second) system, h = 4.135667662 * 10<sup>-15</sup> eV.s (eV.s = electron volt – second)

In terms of E­<sub>p </sub>. t<sub>p </sub>, h = 2pi

APPLICATIONS –

Planck’s constant is used in –

· Photoelectric effect, in the formula – E = h * f

· In atomic structure, in the formula for energy of n<sup>th</sup> orbit

· In uncertainty principle, in the formula for relation between position and momentum

· In de- Broglie wave equation