Two thin lenses, when in contact, produce a combination of power + 10 D . When they are 0.25 m apart, the power reduces to + 6 D . The focal lengths of the lenses (in m ) are
Text Solution
Verified by ExpertsThe correct answer is:
A
When lenses are in contact
..... (i)
When they are distance d apart
..... (ii)
From equation (i) and (ii) 
..... (iii)
From equation (i) and (iii) 
..... (iv) 
Also 
Hence 
⇒ ⇒ 
..... (v)
On solving (iv) and (v) 
and 
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