An object is placed 200 cm from a screen.When a converging lens is placed between the object and screen at a distance of 160 cm from the object,an image is formed on the screen.Without moving the object or screen,an image can also be formed on the screen when the distance from the object to the lens is
A)8 cm
B)16 cm
C)20 cm
D)32 cm
E)40 cm

Question

Quizplus · Accepted Answer

The lens formula is 1/f = 1/v + 1/u. For the first position, u = 160 cm and v = 40 cm (since the total distance is 200 cm). For the second position, the lens equation must still satisfy 1/f = 1/v + 1/u with v = 200 - u. Solving gives u = 40 cm.

An Object Is Placed 200 Cm from a Screen