Question

Find the distance between two possible positions
of a real object in front of a convex lens of focal
length 15 cm such that the size of image is
double the size of object.​

Answer 1

focal length = f= 15 cm

height of image = 3 × height of object

q=3p

p=?

1/f = 1/p +1/q. ( formula)

1/15 = 1/p + 1/3p

p = 15(4)/3

p= 20 cm. answer