Question

a light candle,placed on a metre scale at 8cm mark. was focused on a white screen placed at 92cm mark. using a converging lens placed on the scale at 50cm mark. with the of this data he find that focal lenght of the giving converging lens is 21cm. (A) find he position of image formed if shifted toward the lens at a position of 29cm.(B) state the nature of image formed if the object is further shifted towards the lens.

Answer 1

the position is 45 and the nature of image is real and inverted

Answer 2

Answer:

.

Object distance, u = -(50 – 8) = -42 cm

Image distance, v = (92 – 50) = 42 cm

Now,

1/f = 1/v – 1/u

=> 1/f = 1/42 + 1/42

=> f = 21 cm

2.

When the object is shifted to position 29, the new object distance is, u = -(50 – 29) = -21 cm

That means the object is placed at the focus. So, the image will be formed at infinity.

1/f = 1/v – 1/u

=> 1/21 = 1/v + 1/21

=> v = infinity

3.

If the object is further shifted towards the lens, the object distance becomes less than focal length and it lies between focus and pole of the lens. So, the image formed will be virtual, erect and magnified. The image lies on the same side of the object.