﻿
Question
Mon January 14, 2013 By: Rishav Singh

# A convex lens of focal length 20 cm is placed at adistance of 24 cm from the screen.How far from the lens should an object be placed so as to form real image on the screen.

Mon January 14, 2013

Given,

v(image distance on screen)= 24cm

f= 20cm

Using lens formula,

1/v-1/u=1/f

=> 1/v-1/f=1/u

=> 1/24-1/20 =1/u

=> 5-6/120= 1/u

=> -1/120 = 1/u

=> -120cm =u

Therefore Object distance must be 120 cm from the lens.

Now Magnification,

m=v/u

=> m= 24/-120

=> m= -1/5

=> m=0.2

Thefore image is real, inverted, diminished(smaller) 5 times and object in turn is placed 120 cms in front of the lens

Related Questions
Wed February 15, 2017

# in an experiment the focal length of a convex lens a student obtained a sharp and inverted image of a distant tree on the screen behind the lens.she then removed the screen and looked through lens in the direction of the object .she will see a) an inverted image of the tree at the focus of the lens b)no image as the screen is removed c) a blurered image on the wall of laboratory d0 an erect image of the tree on the lens pls explain me the answer elaborately

Sun January 29, 2017

﻿