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**Thank you all for any help or advice you can give.**

1. Homework Statement

1. Homework Statement

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

## Homework Equations

WFE=2*SFE

## 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.