Thank you all for any help or advice you can give. 1. The problem statement, all variables and given/known data What is the fabrication Wavefront error (WFE) of a mirror with a PV surface error of 1 um? Express your answer in terms of RMS waves at lambda = 0.633 um 2. Relevant equations WFE=2*SFE 3. The attempt at a solution I know to start by calculating the WFE. I know the SFE=1um WFE=2*1um WFE=2um PV I dont know how to convert PV into RMS. Everything I've read says there is no set ratio between PV and RMS measurements. But that values from 3-5 are commonly used depending on the surface error. So I'm a little confused. Thank you again for any help you can offer.