Question

an image 2/3 of the size of the object is foemed by a convex lens at a distance of 12cm find the focal length of lens

Answer 1

Magnification = image distance ÷ object distance

Object distance = u

Image distance = v

Magnification = m

m = v / u

Calculating u we have :

2/3 = 12 / u

u = 12 × 3/2 = 18cm

The lens formula :

1/f = 1/u + 1/v

Where f is the focal length.

Substituting the values into the formulae :

1/f = 1/18+ 1/12

Lcm = 36

1/f = ( 2 + 3)/36

1/f = 5/36

F = 36/5

f = 7.2cm.

Answer 2

Is it right.....

if it is incorrect. tell me correct ans