Focal Length by an Image of far distance object for std 8 to 10

To determine the focal length of a convex lens by obtaining an image of a far distance object. 

AIM : To determine the focal length of a convex lens by obtaining an  image of a far distance object.

PRINCIPLE :  Rays parallel to the axis, after being refracted by a convex lens, are focused on the principal focus. Distance   between the optical centre and the principal focus is known as the focal length.

APPARATUS   :   Convex lens, Stand, Screen, Foot-rule, etc,.

Focal length of a  far distance object

Observation : Distance between the optical center of the lens and the image on the screen = Focal length of the lens  f =   cm...         

Practical uses : Convex lens of proper focal length are used in optical instruments like simple microscope, compound microscope, telescope, etc,. Also the method given here in the simplest way to estimate the focal length of a convex lens.