Question

Find the focal length of a lens in a compound lens system.

• A. \( \frac{1}{f_{total}} = \frac{1}{f_1} + \frac{1}{f_2} \)
• B. \( \frac{1}{f_{total}} = \frac{1}{f_1} - \frac{1}{f_2} \)
• C. \( f_{total} = f_1 + f_2 \)
• D. \( f_{total} = f_1 - f_2 \)

Hint:

When two lenses are in contact, use the reciprocal rule: \( \frac{1}{f_{total}} = \frac{1}{f_1} + \frac{1}{f_2} \). This is essential for calculating the total focal length.