Problem we are looking at :A laser beam has diameter 1.30 mm . The beam exerts a force of 3.7×10−9 N on a totally reflecting surface. What is the amplitude of the electric field of the electromagnetic radiation in this beam? (Emax) Relevant Formulas...etc.: I have the formula I=(Emax)^2/(2*c*u) .. where c is the speed of light (3E8) and u is (4piE-7) I= P/A , where I= intensity My attempt at the problem: I am stumped because the problem would be easy if I was given a power although looking at the problem I am not given power, rather, I am given a force . Do I just substitute P(power)= F(force)*C(speed of light) - Then from there plug (F*C)/A into the I(intensity) for E max.