Question

What is lens maker's formula?

• A. \(\frac 1f=(n-1)(\frac {1}{R_1}+\frac {1}{R_2})\)
• B. \(\frac 1f=(n-1)(\frac {1}{R_1}-\frac {1}{R_2})\)
• C. \(\frac 1f=(n+1)(\frac {1}{R_1}+\frac {1}{R_2})\)
• D. \(\frac 1f=(n+1)(\frac {1}{R_1}-\frac {1}{R_2})\)

Answer 1

The Correct Option is B

To solve the problem, we need to identify the correct form of the lens maker's formula.

1. Lens Maker's Formula:
The lens maker's formula relates the focal length \( f \) of a lens to its refractive index \( n \) and the radii of curvature of its two surfaces, \( R_1 \) and \( R_2 \). The general form of the lens maker's formula is:

\[ \frac{1}{f} = (n - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right) \] where: - \( n \) is the refractive index of the material of the lens, - \( R_1 \) is the radius of curvature of the first surface, - \( R_2 \) is the radius of curvature of the second surface, - \( f \) is the focal length of the lens.

2. Comparing with Given Options:
- Option (A) is correct as it matches the standard form of the lens maker's formula.

Final Answer:
The lens maker's formula is \( \frac{1}{f} = (n - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right) \) (Option A).