Question

Convex lens forms in image 16 cm long of an object 4 cm long kept at a distance of 6 cm from the lens what is the focal length

Answer 1

h'= -16cm
h= 4cm
u= -6cm
f= ?

h'/h = -v/u

-16/4 = -v/-6

-16×-6/4 = -v

v = -24

1/f = 1/v + 1/u

1/f = 1/-24 + 1/-6

1/f = 1/24 + 1/6

1/f = 1+4/ 24

1/f = 5/24

f = 25/5