1. The problem statement, all variables and given/known data You use a sequence of ideal polarising filters, each with its axis making the same angle with the axis of the previous filter, to rotate the plane of polarisation of a polarised light beam by a total of 45°. You wish to have an intensity reduction no larger than 10%. What is the angle between multiple polarisers? 2. Relevant equations I=Imaxcos2(θ) 3. The attempt at a solution For multiple polarisers I=Imaxcos2*n(θ/n) where n is an integer So I=cos2*n(θ/n) with I>0.9 The only integer solutions I was able to obtain was 9 polarisers separated by 5 degrees (n=9). This would give I=0.933 which is less than 10% loss if Imax=1. However, this doesn't appear to be giving me the correct solution. What am I missing?