Question

A student focused the image of a candle flame placed at 2 m from a convex lens of focal length 10cm, on a screen. After that he moves gradually the flame towards the lens and each time focuses its image on the screen

(A) In what direction does he move the lens to focus the flame on the screen?
(B) What happens to the size of the image of the flame formed on the screen?
(C) What difference is seen in the intensity (brightness) of the image of the flame on the screen?
(D) What is seen on the screen when the flame is very close (at about 5cm) to the lens?

Can you also give the reasons please?

Answer 1

1 he move towards the direction in which the lens is placed.
the size will get decrease as the magnifiction obtained is less than 1

Answer 2

(a) The student moves the lens away from the screen to focus the image because on moving the candle towards the lens, the image distance increases.

(b)The size of the image increases when the object is moved towards the lens.

(c) Intensity of the image decreases.

(d) When the candle is moved very close to the lens, no image is formed on the screen. A virtual image is formed behind the candle on the same side of the screen.