# A bi-convex lens is formed with two thin plano-convex lenses as shown in the figure. Refractive index n of th efirst lens is 1.5 and that of the secon

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A bi-convex lens is formed with two thin plano-convex lenses as shown in the figure. Refractive index n of th efirst lens is 1.5 and that of the second lens if 1.2 Both the curved surfaces are of the same radius of curvature R=14cm.  For this bi-convex lens, for an object distance of 40cm, the image distance will be

A. .280.0cm
B. 40.0cm
C. 21.5cm
D. 13.3cm

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(1)/(f_(1))=(1.2-1)((1)/(oo)-(1)/(-14))=(0.2)/(14)
(1)/(f_(2))=(1.5-1)((1)/(14)-(1)/(oo))=(0.5)/(14)
(1)/(f_(eq))=(0.7)/(1.4)=(1)/(20)
(1)/(v)-(1)/(-40)=(1)/(20)
v=40cm