Let E_0 and B_0 denote the amplitude of electric and magnetic field...

Intensity of electromagnetic wave, I=$\frac{1}{2} \varepsilon_0 E_0^2 c=$\frac{1}{2} \frac{B_0^2 c}{\mu_0}$where,$B_0=$electric field and$c=$speed of light. Now, momentum transfer per unit area per unit time, which is also called radiation pressure.$\begin{gathered}\frac{1}{A}\left(\frac{\Delta p}{\Delta t}\right)=\frac{I}{c}=\frac{\frac{1}{2} \varepsilon_0 E_0^2 c}{c}\\ \frac{I}{c}=\frac{1}{2} \varepsilon_0 E_0^2 \end{gathered} [where, $\Delta p=$ momentum transferred, $\Delta t=$ time and $A=$ area.]