Pick a topic on the left, open a problem and check the solution hint by hint.
An object is placed at a distance $d = 20$ cm from a diverging lens of focal length $f = -10$ cm. Find the image distance and state what kind of image it is.
An object is placed at a distance $d = 30$ cm from a converging lens of focal length $f = 10$ cm. Find the distance $d'$ from the lens to the image of the object.