Question

Rohit focused the image of a candle flame on a white screen using a convex lens.He noted down the position of the candle ,screen and lens as under:
position of candle =26.0 cm
position of convex lens =50.0 cm
position of screen =74.0 cm
i) what is the focal length of the convex lens?
ii) where will the image be formed if he shifts the candle towards the lens at a position of 38 cm?
iii) draw a ray diagram to show the formation of the image in case (ii) as said above?

Answer 1

I hope it will help you....

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.