Question

What is Lens Formula?

Answer

Lens Formula - focal length of the lens is given by, 1/f = (μ₂/ μ₁ - 1) (1/ R₁ - 1/ R₂) where, R₁ and R₂ are the radii of curvature of first and second refracting surfaces of a thin lens, f is the focal length and μ is refractive index of material of lens with respect to surrounding medium as shown in the figure given below. If μ₂ and μ₁ = 1, then ⇒ [1/f = (μ - 1) (1/R₁ - 1/R₂)] This is called lens maker Formula. Lens maker formula is used to design lenses of desired focal length. Lens formula is given by 1/v - 1/u = 1/f