Question

The focal length of the symmetrical convergent lens is 25cm. what is the radius curvature of the lens?​

Answer 1

Explanation:

Using lens-maker formula :               f1=(μ−1)(R11−R21)

For convex lens :        R1=R             R2=−R

∴      f1=(μ−1)(R1−−R1)             ⟹     f1=(μ−1)R2           ........(1)

For plano-convex lens :        R1=R             R2=∞

∴      f′1=(μ−1)(R1−∞1)             ⟹     f′1=(μ−1)R

Answer 2

The radius curvature of the lens is 50 cm.

Explanation:

The focal length and radius of curvature relationship is given as:

f = R/2

Where,

f = Focal length = 25 cm (given)

R = Radius of curvature

Now, on substituting the values in the formula, we get,

25 = R/2

R = 25 × 2

∴ R = Radius of curvature = 50 cm