Asmall laser used as a pointer produces a beam of red light 5 mm in diameter, and has a power output of 5 milliwatts. what is the magnitude of the electric field in the laser beam?

434.0 V/m

Explanation:

The power output of the laser is:

while the radius of the beam is

so the cross-sectional area is

So the intensity of the laser beam is

The intensity of a laser beam is related to the magnitude of the electric field by

where

c is the speed of light

is the vacuum permittivity

Solving the formula for E, we find

where are the vectors ?

i don't understand. explain it clearly