an electro magnetic wave has an electric field given by E= (3.1x10^5 v/m)*khat*Cos[ky-(12.65*10^12 rad/s)t]
k = 2pi/(lambda)
The Attempt at a Solution
I do not know what to sub in for y and t or how to set the equation equal to something so i can solve. So I am pretty much stuck.