Ey = 375 cos [ kx - (92.20x10^14).t ]
the formula of the electric field of an electromagnetic wave :
=> Ey = Emax cos (k x - ω t)
=> Ey = Emax cos [(2π/λ) - (2π f).t ]
then : (2π f).t = (92.20x10^14).t
===> 2π f = 92.20x10^14
===> f = 92.20x10^14 / 2π
===> f = 1.46 x 10^15 hertz
the speed of electromagnetic wave : c = 3 x10^8 m/s
then : c = f λ
======> λ = c / f
======> λ = 3 x10^8 / 1.46 x 10^15
======> λ = 2.0547 x 10^-7 meters = 0.205 μm
