Question

Which of the following does not affect the focal length of a convex lens?

• A. Refractive index of the material making the lens
• B. Material of the lens
• C. Object distance
• D. Thickness of the lens

Answer 1

The correct option is C Object distance

$\text{we know,}$

$\frac{1}{f}=(\mu -1)(\frac{1}{R_1}-\frac{1}{R_2})$

$\begin{array}{c}f\to \text{focal length}\\ \mu \to \text{refractive index of lens}\\ \text{w.r.t medium}\\ R_1,R_2\to \text{radius of curvatures}\\ \text{f}\text{does not depend on the}\\ \text{object distance.}\end{array}$