High School Physics

Lens Formula | Spherical lens formula

Last updated on June 15th, 2023 at 04:55 pm

Lens Formula – A formula that gives the relationship between image distance (v), object distance (u), and focal length (f ) of a lens is known as the lens formula. This lens formula applies to both types of spherical lenses: convex lenses as well as concave lenses.

Lens Formula | spherical Lens equation

The lens formula can be written as :
1/v – 1/u = 1/f
where v = image distance,
u = object distance,
and f = focal length.

See solved Lens numerical problems here.

Difference between the Lens formula and the Mirror formula

Please note that the lens formula differs from the mirror formula only in the sign between
1/v and 1/u .

The mirror formula is 1/v + 1/u = 1/f whereas the lens formula is 1/v – 1/u = 1/f.

It is clear that the mirror formula has a plus sign (+) between 1/v and 1/u whereas the lens formula has a minus sign (–) between 1/v and 1/u.

The values of v and u should be substituted in the lens formula with their proper signs.