A spherical lens is used to obtain an image on a screen. The size of the image is four times and size of the object . What is the type of lens and at what distance is the screen placed from the lens ?

A spherical lens is used to obtain an image on a screen. The size of t

1.	A spherical lens is used to obtain an image on a screen. The size of the image is four times and size of the object . What is the type of lens and at what distance is the screen placed from the lens ?
Answer» Solution :Data : `M=-4`, TYPE of lens ?V=? As the iamge FORMED by the lens is obtained on a screen , it is a real image. The lens is , therefore, a convex lens. `M=-4 v/utherefore u=-v/4` `1/f =1/v- 1/u=1/v-(1)/((-v//4))=1/v+(4)/(v)=(5)/(v)` `therefore v=5f` The DISTANCE of the screen from the lens =5f.