1. The problem statement, all variables and given/known data Light of wavelength 5000 angstroms is incident normally on a series of two transparent plastic disks separated by a distance large compared with the wavelength. If the index o refraction of the disks is n=1.5, what fraction of the light is transmitted? Neglect absorption, internal multiple reflections, and interference effects. 2. Relevant equations T = 1+R R = (n1-n2)/(n1+n2), where n is the index of refraction depending on the material Itotal is proportional to |Etotal|^2 = Etot * (Etot*) where (Etot*) is the complex conjugate. 3. The attempt at a solution R = (1-1.5)/(1+1.5) = -0.20: going from air to the disk1 Similar calculations for air to disk1, disk1 to air, air to disk2, and disk2 to air. I tried to calculate Etotal as: Etotal = -0.20*E0 + 0.20E0* e^(i*delta) delta = 2kd = 2*(2pi/lambda)*d where d = thickness of the disc but I am not given a thickness... Am I missing an equation I need to use? Approaching this from the wrong angle? Any advice would help! Thank you.