# WFE of a Mirror

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

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

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.

## Answers and Replies

I don't know much about optics, but to me it seems like the problem statement is missing some context.

There isn't any mention of a specific type of surface aberration, or perhaps some kind of approximation based on some assumptions you've discussed in your course?

Thank you for the response.
I feel the same way thats why I was asking. There is no mention of specific type of aberration in the question, and as far as I can tell from the reading you can use any number between 3-5 depending on the different aberration you are dealing with. I was hoping someone was familiar with optical engineering and could let me know what I'm missing. Thanks again.