The magnetic field vec$($B$)($z$,$t$)$ of a plane monochromatic

electromagnetic wave of wavelength $\backslash$lambda $=685$nm that is

propagating in a vacuum in the z direction is described by:

vec$($B$)($z$,$t$)=$B$\_(1)$sin$($kz$-\backslash$omega t$)($hat$()+$hat$())$

where B$\_(1)=5\mathrm{.}00\backslash$times $10^(-6)$T$,$ and hat$()$ and hat$()$ are the unit vectors

in the positive$-$ x and positive$-$ y directions, respectively.