Introduction to Dirac's constant: Difference between revisions

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'''Dirac's constant''' is also known as the "reduced Planck's constant." It is a natural constant that is involved in many [[quantum mechanics|quantum theoretical]] equations.

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The reduced Planck's constant appears more often than ''h'' in the algebra of QM for many reasons, one of which is that angular velocity or angular frequency is ordinarily measured in radians per second, so using ħ eliminates converting radians into degrees or vice-versa. Also, when QM equations are written in terms of ħ, the frequent 2π factors in numerator and denominator often cancel. However, in other cases, as in the orbits of the Bohr atom, ''h''/2π arises naturally from the algebra of orbital [[angular momentum]].

The numerical value of ''h'' depends on the choice of units in which energy and wavelength are measured. If energy is measured in [[electron volt]]s (eV, a common practice in [[particle physics]]) and wavelength is measured in [[ångström]]s (10^-10−10[[meter|m]]), then the energy of a photon is approximately ''E''_{<small>eV</small>} = 12400/λ_ångström. This form is easily remembered and avoids the small values of SI units.<ref>A. P. French and Edwin F. Taylor, ''An Introduction to Quantum Physics,'', p. 18.</ref>

==References==

{{Reflist}}

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[[Category:Quantum mechanics]]