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Grade: 12

Diameter of a Plano-convex lens is 6 cm and the thickness at the center is 3 mm. If the speed of light in the material of the lens is 2 x 10^8 m/sec, what is the focal length of the lens?

8 years ago

Answers : (2)

vikas askiitian expert
509 Points

diameter = 2 Radius (R)

 2R = 6

 R = 3cm

1/f = (u-1)/R      ......1      

this is the relation bw focal length of plano convex lens & u(refractive index) ...

u = c/v = 3*108/2*108 = 1.5

now put u in eq 1 , will get focal length

8 years ago
vineet jakhar
33 Points
							radius will be 15 not 3! use geometry. let (x) be radius of curvature .BASE- (x-3) HEIGHT -(3) HYPOTANEOUS -(x) solve and get (x)!    :)
one year ago
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