Question

A student wants to project the image of a candle flame on the walls of school laboratory by using a lens : 

(i) Which type of lens should he use and why ? 

(ii) At what distance in terms of focal length 'F' of the lens should he place the candle flame so as to get (i) a magnified, and (ii) a diminished image respectively on the wall? 

(iii) Draw ray diagram to show the formation of the image in each case ?

Answer 1

(i) He should use a convex lens as it forms real images. 

(ii) He should place the candle flame between F and 2F (the focus and centre of curvature of the lens) to get the magnified image on the wall while the diminished image is obtained when the object is located at a distance greater than 2F. 

(iii) The ray diagram for the formation of the magnified image is shown below :

The ray diagram for the formation of the diminished image is shown below :