Question

The radius of curvature of spherical surfaces
of a convex lens 15 cm. and 10cm respectively.
If Refractive Index of lens is 1.5, then find
its focal length​

Answer 1

Answer:

focal length = 12 cm.

Explanation:

FORMULA:        $\frac{1}{f}=($ μ $-1)(\frac{1}{R_{1} }-\frac{1}{R_{2} })$

Here,

$f=?\\R_{1}=+15 cm\\R_{2}=-10cm$

 μ = 1.5

Substituting,    $\frac{1}{f}= (1.5-1) (\frac{1}{15 } -\frac{1}{-10} )$

                            =  $(0.5)(\frac{1}{15}+\frac{1}{10} )$

                            =  $(0.5)(\frac{1}{6} )$

                         $\frac{1}{f} =\frac{1}{12}$

            Therefore, $f = 12 cm.$