Question

Two lenses have power +20&-40. What is the nature & focal length of each lens?An object is kept at 100cm from the lens power -40. Calculate the image distance ​

Answer 1

Answer:

The value of magnification for convex lense is 1 and for concave lens is 0.2

Explanation:

Given data:

Power of lenses: +2D and - 4D

+2D indicates that the lens is converging

lens (convex lens)

Distance of object p =1/f

Focal length f= 50 cm

i)-4D indicates that the lens is diverging lens

(concave lens)

Therefore the focal length is -25 cm

*To calculate the image distance for

convex lens

u = -100 cm

f 50 cm

V= (fx u)/(f-u) = 100 cm

V= -(fx ul/(f+u)

V -20 cm

magnification =v/u = 20/100 =0.2