"Intensity of Incoherent EM Waves

[rachiebaby17]

Homework Statement

Two incoherent EM waves of intensities 7I0 and 13I0 travel in the same direction in the same region of space. What is the intensity of EM radiation in this region?

Homework Equations

The Attempt at a Solution

I have tried using I = I1 + I2 + ( 2* square root of (I1 * I2))
also tried using the same equation with a minus sign in front of the () portion.

I am lost at what I need to do even some hints would be so great!

 

[rl.bhat]

I have tried using I = I1 + I2 + ( 2* square root of (I1 * I2))
This formula is true only for coherent sources not for incoherent sources.
For incoherent sources you can directly add the intensities.