Herttzian Mechanics (contd...)

We further introduce an equivalent radius defined by

	(5.7)

So far in our discussions we have considered only convex surface, which has positive radius. But it is applicable also for concave or saddle surface, with a negative sign to the radius of curvature.

It is evident from equation 8.5 that contours of constant gap between the two surfaces is an ellipse with, the length of axes are in the ratio .

Let's say two cylindrical lenses each with radius , and then and , i.e. .

Thus, the relative radii of curvatures are, and .

The equivalent radius and

This is the ratio of major to minor axes of the contours of constant separation as discussed earlier.