Uncertainty relations in classical and quantum theories of electromagnetism

Sharp uncertainty relations restricting the values of variances in the position space and in the momentum (wavevector) space are derived. They have the same form $\mathrm{\Delta }r\mathrm{\Delta }k\ge 5\mathrm{/}2$ in the classical theory of light beams, in the quantum theory of coherent light beams, and in the quantum theory of individual photons.