The given lens is broken into four parts and rearranged as shown. If the initial focal length is f and initial intensity of image is I, then after rearrangement the equivalent focal length and intensity of image is?
Text Solution
Verified by ExpertsThe correct answer is:
B
Each part has a focal length = 2f
∴ 
= 
+ 
+ 
+ 
= 
+ 
+ 
+ 
= 
∴ F = 
Since the area of the lens exposed to incident light is half of the original and since intensity of image is proportional to area of the lens.
∴ intensity of image becomes half of the initial
∴ I ′ = I/2
Therefore the answer will be .
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