IMAGE OF BULB FIXED AT WALL OF ROOM IS TO BE OBTAINED ON OPPOSITE WALL 3METRE AWAY BY MEANS OF A CONVEX LENS. NOW FIND THE FOCAL LENGTH, IMAGE DISTANCE, OBJECT DISTANCE.

Asked by IOUHIU OYYFGY | 17th Nov, 2010, 03:19: PM

Expert Answer:

Dear student

Let the object be at a distance x from the lens and image at ( 3 - x)

u = -x and v = 3 - x

F is +ve

1/v - 1/u = 1/ f

or, 1/ (3-x) + 1/ x = 1/f

or, f = [x ( 3 - x) ]/3..............(i)

3f = 3x2 - x2

For real roots, discriminant is greater bthan or equal to zero;
so solving above equation, we get f = 0.75 m
By putting this value of f in equation (i), the object distance and image distance can be calculated.
 
We hope this clarifies your doubt.
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Topperlearning

Answered by  | 18th Nov, 2010, 06:29: PM

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