پایای ِ ساختار ِ نازک pâyâ-ye sâxtâr-e nâzok
*Fr.: constante de la structure fine*
A measure of the strength of → *interaction*
between a → *charged particle* and the
→ *electromagnetic field*. It is a
→ *dimensionless* number
expressed (in → *cgs unit*s) by
α = *e*^{2}/ħ*c*, where *e* is the
→ *electron charge*, ħ is the
→ *reduced Planck's constant*, and *c* is the
→ *speed of light*. It is
approximately equal to 1/137 or 7.3 x 10^{-3}.
The smallness of this number is of great importance since it determines the size of
→ *atom*s and the → *stability*
of → *matter*. → *fine structure*; → *constant*. |