This would also be about the focal length of the finished lens.
B is a double convex lens, which has a focal length of twenty inches.
Its focal length of 30 feet can be increased to 108 feet by a Cassegrainian combination.
What is the aperture, focal length, and name of maker of your telescope?
The power may also be obtained by dividing 39.37 by the focal length in inches.
In a double and equally convex lens of glass the focal length is equal to the radius of the spherical surfaces of the lens.
If the lens is a plano-convex the focal length is twice the radius of its spherical surfaces.
The focal length of the lens was 150 feet, and the mirror was placed about 15 feet within the principal focus.
As the diameter of the lens was so small in comparison with its focal length, its want of achromatism was inappreciable.
In this case it is said that the lens having a focal length of one inch magnifies ten times, or has a power of ten.
focal length n.
The distance from the surface of a lens or mirror to its focal point. Also called focal distance, focus.