 # One side of radius of curvature R2=120cm of a convexo-convex lens of material of refractive index n=1.5 and focal ength f1=40 cm is silvered. It is placed on a horizontal surface with the silvered surface in contact with it.Another convex lens of focal length f2=20cm is fixed coaxially d=10cm above 1st lens.A point object on axis give riseto an image coincident with it.Findthe height of the object above the upper lens

11 years ago

Dear student,

##### Let AB represent an object placed at right angles to the principal axis at a distance greater than the focal length f of the convex lens. The image A1B1 is formed beyond 2F2 and is real and inverted.

OA = Object distance = u

OA1 = Image distance = v

OF2 = Focal length = f OAB and OA1B1 are similar  But we know that OC = AB the above equation can be written as  From equation (1) and (2), we get   Dividing equation (3) throughout by uvf  All the best.

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