Peak electric field of a laser light.

[Roflcopters]

Homework Statement

A laser produces an average power of 7.0 W in a light beam 1.0 mm in diameter. Find (a) the average intensity and (b) the peak electric field of the laser light

Homework Equations

Intensity = P/ A
Unsure about part B

The Attempt at a Solution

For part A I did P/( ∏ * r^2) which came to be 7W/( ∏ * .0005^2) which came to 8912676 w/m^2

But I need help finding out how to do part B. Any help would be great.

 

[Delphi51]

This should give you the relationship between Electric field and intensity.
http://en.wikipedia.org/wiki/Intensity_(physics)