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Formula Biconcave Lens Focal length    Refractive index of the medium    Right radius of curvature   

Formula
Formula: Biconcave Lens
Biconcave Lens With Radius of Curvature and Focal Length

Focal length

Unit
Focal length is the distance between the lens (or the principal plane for a thick lens) and the focal point. For a biconcave lens, the focal length is negative. For a biconvex lens it is positive.

Refractive index of the medium

Unit
Refractive index of the medium outside the lens. If the lens is in the air, then \( n_{\text M} \approx 1 \).

Refractive index of the lens

Unit
Refractive index of the material from which the lens is made.

Right radius of curvature

Unit
Right radius of curvature \(R_1\) of the biconcave lens (see illustration).

Left radius of curvature

Unit
Left radius of curvature \(R_2\) of the biconcave lens (see illustration).