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A converging lens is kept coaxially in c...

A converging lens is kept coaxially in contact with a diverging lens, both the lenses being of equal focal lengths. What is the focal length of the combination?

Text Solution

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`(1)/( f) = ( 1)/( f_(1)) + ( 1)/( f_(2))`
`= ( 1)/( f_(1)) + ( 1)/( -f_(2)) ` `( :. f_(1) = - f_(2))`
`rArr f = oo`
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