Question

The given lens is broken into four parts and rearranged as shown. If the initial focal length is \( f \), then after rearrangement the equivalent focal length is – 

• A. \( f \)
• B. \( \frac{f}{2} \)
• C. \( \frac{f}{4} \)
• D. \( 4f \)

Hint:

When combining multiple lenses in series, the equivalent focal length is the reciprocal of the sum of the reciprocals of the individual focal lengths.

Answer 1

The Correct Option is B

Step 1: Understand the lens formula.
For a combination of lenses in series, the equivalent focal length \( \frac{1}{f_{\text{eq}}} = \frac{1}{f_1} + \frac{1}{f_2} + \cdots \).
Step 2: Rearrange the parts of the lens.
When the lens is broken and rearranged, the effective focal length is halved. Final Answer: \[ \boxed{\frac{f}{2}} \]