# A point source is located at a distance of 20cm from the front surfaceof a gllass bi convex lens.the lens has thickness of 5 cm. the refractive index of glass is 1.5. the distance of image formed by it from the rear surface of this lens is

1
by deetkankatilpa
you need to give the radii of curvature of the surfaces of the lens

2015-11-12T02:53:20+05:30

### This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
We need the radii of surfaces of lens R1 and R2.  I am giving the formulas and the procedure here.  So follow these steps.

1) Formulas:

Back Effective focal length to focus F' = B EFL = f '  (+ve)
Effect focal length in front of the front surface =  EFL = f (-ve)

R1 = +ve          R2 = -ve
Thickness of the lens = d
μ = refractive index of the lens wrt air (medium) around the lens on both sides

Frontal focal length (distance) from surface to Focus F = FFL = -ve
Back Focal length (distance) from back surface to Focus F' = BFL = + ve

2. Given values:

Given R1 = R2,  d = 5 cm,  μ = 1.5 ,  u = - 20 cm

3. Procedure:

1)  Find  f  =  f'
2)  Then  find v from the formula 1/f = 1/v - 1/u
3)  From   v now subtract  (f'  -  BFL)  to get the distance of image from the rear surface.  This value of (f ' -  BFL)  or  (f  -  FFL)  may be close to  d/2.

click on thanks button above ;;; select best answer