Question

(a) The focal length of a convex lens is 20 cm. At what
distance an object be placed from this lens so that
the image is formed twice the size of the object
while image is real ?
​

Answer 1

Answer:

draw a line 20 cm to lens then point it on the point of circumference

at the principle axis

from focus

the image which will form will be doubled size mark it as A and b '

then you will get you answer or just focal length r/2