Similarly, drops transmitting rays after two internal reflections will be situated on covertical and coaxial cones, of which the semi-vertical angles are 51° for the red rays and 54° for the violet.
Capacity of two concentric spheres, of two coaxial cylinders and of two parallel planes.
The same arrangement can be supplied to a pair of coaxial cylinders.
The other case of importance is that of two coaxial cylinders.
Let a solid circular sectioned cylinder of radius R 1 be enclosed in a coaxial tube of inner radius R2.
The isothermal surfaces are coaxial cylinders.