Question

A convex lens of focal length f is placed somewhere in between an object and a screen . The distance between the object and a screen is X. If the numerical Value of the magnification produced by the lens is m, then the focal length of lens is? ​

Answer 1

Explanation:

Correct option is

A

(m+1)

2

mx

If we consider that the object is placed at a distance u from the lens, then object distance =−u

This gives, u+v=x

Also, magnification, m=

−u

−v

=

u

v

Now, using the lens formula,

v

1

−

−u

1

=

f

1

Solving these 3 equations simultaneously, we get:

f=

(m+1)

2

mx