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Two thin lenses of focal length +10 cm -...

Two thin lenses of focal length `+10` cm -5 cm are kept in contact. What is the (i) focal length and (ii) power of the combination ?

Text Solution

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`f_1`=+10 cm
`f_2`=-5 cm
`1//f=1//f_1+1//f_2`
1/f=-1/10
f=-10 cm
Power =1/f
100/f(in cm)
P=-100/10=-10 D
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