What is the maximum value of the electric field in an electromagnetic wave whose average intensity is 4.50 w/m2?

Average intensity of electromagnetic wave is given by

I = (speed of light*permittivity*sq. electric field) / 2

Speed of light = 3x10^8 m/s

Permittivity = 8.85x10^-12

Therefore,

Electric field = sqrt (2I / (speed of light xpermittivity)) = sqrt ((2*4.50) / (3*10^8*8.85*10^-12)) = 58.22 V/m