CD's as parabolic mirrors?

From: Dwight Elvey <elvey_at_hal.com>
Date: Mon Dec 11 17:51:31 2000

Dwight Elvey <elvey_at_hal.com> wrote:
> If one only looked at warping, it would only take about
> 0.060 of a depression of the center to cause a 20 foot focal
> length.

Oops!
 Error in my calculation:
 It should have been 0.005 inches.

 Formula for saggitta is

   r^2/4f = s

 In this case r ~= 4.5/2 inches
              f ~= 20 feet ( 240 inches )

 go figure!
Dwight
Received on Mon Dec 11 2000 - 17:51:31 GMT