Question

1. When an object is placed at a certain distance from a convex lens of focal length 30cm a
real image magnified 3 times is formed. What is the distance of the object?
a.
20 cm b. 40 cm c. 30 cm d. 50 cm​

Answer 1

As we know

magnification = -3

( - ) bcs real image

and by putting formulae

m = F / ( F - U )

-3 = 30 / ( 30 - u )

( 30 - u ) = - 10

U = +40 cm