An image of an object is formed on a screen by a lens. Leaving the lens fixed the object is moved to a new position and the screen moved until it again receives a focused image. If the two object distances are pi and p2, and if the transverse magnifications of the images are M1 and M2, respectively, show that the focal length of the lens is given by (P2 – P1) 1 M1 M2

An image of an object is formed on a screen by a lens. Leaving the lens fixed the object is moved to a new position and the screen moved until it again receives a focused image. If the two object distances are pi and p2, and if the transverse magnifications of the images are M1 and M2, respectively, show that the focal length of the lens is given by (P2 – P1) 1 M1 M2