Zemax Tutorial -3 - Negative lengths when appropriate and when in error

The third Zemax tutorial briefly covers when negative lens are appropriate and when they are errors.
Homework found at www.opticsrealm...
Homework (added after video recorded)
An equi-convex lens with a 10 mm radius of curvature is 2 mm thick and 10 mm in diameter. What is the edge thickness?
What center thickness will make the lens in problem #1 have a 1.5 mm edge thickness?

[@szabolcsspindler1570]

Thank you! This is wht I was looking for!

[@micheleguastamacchia9743]

What is the footprint of a lens? Thank you.

[@fanglinlindaliu4539]

thanks so much!

[@hervevalentin69]

Thanks a lot !!!

[@QuintinMassey]

2:57 trying to understand what you mean by the metal growing faster than the lens and the lens falling through the coating chamber. Do you mean that the metal may expand to a point where it blocks the vapor being deposited on the coating aperture? Hence, not accomplishing the 80/95% ?

[@jihopark9548]

1:25 edge thickness