Question

while the Object is placed at 20cm from the lens, the lens forms Image on a screen twice of its size .
Find it's focal length and nature of the lens .​

Answer 1

Answer:

f=40/3

Explanation:

the object size is 20 cm so the image size will be 40 cm .

using lens formula :- 1/f= 1/v-1/u

1/f=1/40-(-1/20)

1/f=1/40+1/20

1/f=3/40

f=40/3

so the nature of lens is convex