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Findout the equivalent focal length of the combenation of lenses shown in the figure. Surrounding medium is air. |
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Answer» Solution :`1/f =1/v-1/u` `rArr 1/10=1/v+1/15` `rArr 1/v=1/10-1/15` `rArr v=150/5=30` `1/f=1/v-1/u` By differentating : `0=(dv)/(v^(2) dt)-(du)/(dt u^(2))` `rArr 0=- (dv)/v^(2)+(du)/u^(2)` `rArr (du)/u^(2)=(dv)/v^(2)` `rArr (dv)/(du)=v^(2)/u^(2)` `rArr dv =((30)^(2))/((15)^(2))xx(1-2)=-4(1)` `rArr (v_(I)-v_(L))=v^(2)/u^(2) (v_(E)-v_(L))` `rArr (v_(I)-2)=4xx-1` `rArr v_(I)=-2` |
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