light waves

Q1.consider two plane coherent light waves of same frequency (v) and velocity.,incident at a point p.the electric fields associated with the light are given by......

E1=e0cos(on-kz)
E2=e0cos(om-kz+E)

Where E denotes the phase difference between e1 and e2. 2pi v is the angular frequency and the wave number k= 2pi/lamda (lamda is the wave length of light in thek medium considered)

From the principle of superposition the resultant electric field (E) at p given by E=E1-E2
Draw the plot of E1/E0 and E/E0 versus pi at t-0 for the following three cases
A)E=0 or 2pi
B)E=pi
C)E is arbitrary