Question

in a convex lens distance of object is 18 cm and focal lenghth is 20cm. determine magnification in this case

Answer 1

Answer:

By using lens formula

v1−u1=f1

where v=24cm ,f=18cm

241−u1=181

from this we get u=−72cm

magnification of lens is m=uv

m=−7224=−31

Answer 2

u= -18 cm

f = -20 cm

1/f = 1/v - 1/u

1/v = 1/f + 1/u

1/v = 1/-18 + 1/20

1/v = ....

after finding v

by

m= -v/u

and find m