Question

The focal length of a lens depends on

• A. Radius of curvature
• B. Refractive index of the lens
• C. (A) and (B)
• D. None of the above

Answer 1

The Correct Option is C

To solve the problem, we need to determine what factors the focal length of a lens depends on.

1. Formula for Focal Length:
The focal length \( f \) of a lens is given by the lens maker's formula:
\[ \frac{1}{f} = \left( \mu - 1 \right) \left( \frac{1}{R_1} - \frac{1}{R_2} \right) \] where \( \mu \) is the refractive index of the lens material, and \( R_1 \) and \( R_2 \) are the radii of curvature of the two spherical surfaces of the lens.

2. Analyzing the Formula:
From the lens maker's formula, we can see that the focal length depends on two factors:
- The **radius of curvature** of the lens surfaces (\( R_1 \) and \( R_2 \)).
- The **refractive index** (\( \mu \)) of the lens material.

3. Conclusion:
Both the radius of curvature and the refractive index of the lens affect its focal length.

Final Answer:
The focal length of a lens depends on both the radius of curvature and the refractive index of the lens, which corresponds to option (C).