How Does a Spherometer Measure Curvature?

[blackcat]

I'm trying to figure out what/how to use one without seeing/having one.

Am I right in saying the following.

It has three legs, which form the vertices of an equilateral triangle. The centre leg is placed onto a lens, and it's adjusted until they all balance/evne out. Then the distance of it has been adjusted is noted, and put into this formula (on wikipedia I found);

r = [ (a^2 + 3h^2)/6h ]

in which a = distance between feet, and h is the distance it's been adjusted.

Is there a diagrammatical representation of this? Can someone correct any mistakes?

Thanks

 

[OlderDan]

I'm trying to figure out what/how to use one without seeing/having one.

Am I right in saying the following.

It has three legs, which form the vertices of an equilateral triangle. The centre leg is placed onto a lens, and it's adjusted until they all balance/evne out. Then the distance of it has been adjusted is noted, and put into this formula (on wikipedia I found);

r = [ (a^2 + 3h^2)/6h ]

in which a = distance between feet, and h is the distance it's been adjusted.

Is there a diagrammatical representation of this? Can someone correct any mistakes?

Thanks

There are three fixed legs separated by distance a and an adjustable leg in the center of the triangle.

http://physics.kenyon.edu/EarlyApparatus/Optics/Spherometer/Spherometer.html

The flat disk is engraved with the markings to show the d value. The vertical flat is aligned with the markings to read d.