A laser beam, propagating in y direction in air has diameter 2 cm. The power of the laser is 3.14 W. The wavelength of the laser is 630 nm. If the ⃗ -field is oscillating along z direction, write equation for ⃗ -field as a function of (x, y, z, t) inside the beam. Assume B=0 at r = 0, t = 0. While writing the equation, assume the wave is a plane-wave (ignore the fact that the beam has