Question

Suppose you have focussed on a screen the image of candle flame placed at the farthest end of the laboratory table using a convex lens . IF your teacher suggests you to focus the parallel rays on the sun , reaching your laboratory table , on the same screen , what you are expected to do is to move the :- a) Lens slightly towards the screen . b) Lens slightly away from the screen . c) Lens slightly towards the sun . d) Lens and screen both towards sun .

Answer 1

In the case of the candle flame, the object is placed behind c, that means the image is formed or focused between c and f. In second case, the object or sun is at infinity so the image will be formed at focus. This means that the distance between image and lens has decreased in the second case. Either we have to the screen towards the lens or the lens towards the screen.
So, option (a) is right.