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An-object-60cm-tall-is-placed-on-the-principal-axis-of-a-convex-lens-and-its-30cm-tall-image-is-formed-on-the-screen-placed-at-a-distance-of-40cm-from-the-object-What-is-the-focal-length-of-the-lens-




Question Number 51637 by Necxx last updated on 29/Dec/18
An object 60cm tall is placed on  the principal axis of a convex lens  and its 30cm tall image is formed  on the screen placed at a distance  of 40cm from the object.What is  the focal length of the lens?
Anobject60cmtallisplacedontheprincipalaxisofaconvexlensandits30cmtallimageisformedonthescreenplacedatadistanceof40cmfromtheobject.Whatisthefocallengthofthelens?
Answered by aseerimad last updated on 29/Dec/18
Commented by aseerimad last updated on 29/Dec/18
pls verify...i am also a student of this level....
Commented by Kunal12588 last updated on 29/Dec/18
me too (class 11)
metoo(class11)
Commented by aseerimad last updated on 29/Dec/18
is it ok?
Answered by tanmay.chaudhury50@gmail.com last updated on 29/Dec/18
(1/v)+(1/u)=(1/f)  1+(v/u)=(v/f)  1+m=(v/f)  u+v=d  u(1+(v/u))=d  1+m=(d/u)  (1+m)^2 =(v/f)×(d/u)=((md)/f)  f=((md)/((1+m)^2 ))=(((1/2)×40)/((1+(1/2))^2 ))=((20×4)/9)=((80)/9)
1v+1u=1f1+vu=vf1+m=vfu+v=du(1+vu)=d1+m=du(1+m)2=vf×du=mdff=md(1+m)2=12×40(1+12)2=20×49=809

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