. A student focussed the image of an object on a white screen using a converging lens


He noted down the positions of the object, screen and the lens on a scale as given below: Position of object = 10.0 cm

Postion- of lens = 50.0 cm

Position of screen = 90.0 cm

(a) Find the focal length of the converging lens.

(b) Find the position of the image if the object is shifted towards the lens at a position of 30.0 cm.

(c) State the nature of the image formed if the object is further shifted towards the lens. 

 

Best Answer

Ans. Object distance, u = -40 cm Image distance, v = (90 - 50) = +40 cm

(a) Focal length of converging lens, f = ?

According to lens formula:

image of an object

(c) If the object is shifted from 30 cm towards 50 cm, the object lies between the focus and optical centre of the lens. Then the image formed will be behind the object, virtual, erect and enlarged (larger than the object).

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