Question

Rohit focused the image of a candle flame on a white screen using a convex lens He noted the position of the candle , screen,and lens as under
Position of candle=26.0
Position of convex lens=50.0
Position of screen =74.0


1What is the focal length
2where will be the image be formed if he shifts the candle towards the lens at a position of 38 cm
3Draw a ray diagram to show the formation of image in case 1 as said above

Answer 1

24 cm, beyond 12 cm from the lens

Answer 2

Answer:

( i ) .  Object distance u = 50 - 26 = 24 cm

Image distance v = 74 - 50 = 24 cm .

Since object distance is equal to image distance.

2 f = 24

= > f = 12 cm

So , focal length of object is 12 cm.

( ii ) . u = 50 - 38 = 12 cm

It's mean candle is at focus.

= > Image will form at infinity.

( ii ) Refer to attachment for ray diagram.