An object 2.4 m in front of a lens forms a sharp image on a film 12 cm behind the lens. A glass plate 1 cm thick, of refractive index 1.50 is interposed between lens and film with its plane faces parallel to film. At what distance (from lens) should object shifted to be in sharp focus on film ?
Text Solution
Verified by ExpertsThe correct answer is:
D
Initially the object distance is 240 cm and the image distance is 12 cm so
⇒ f = 
due to the slab, the shifting of the image will be:
shift = 1(1 – 
) = 
Now v´ = 12 – 
= 
cm
∴ 
= 
– 
= 
= 
u = 560 cm = 5.6 m
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