If an object is placed 21 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed 19 cm from the lens, the image formed is slightly larger than the object. The approximate focal length of the lens is:
Answers
Given:
Distance of the object from converging lens = d1= 21cm
Distance of the object from converging lens = d2 = 19cm
To Find:
The approximate focal length of the lens
Solution:
When object is placed at a distance of 2f from the lens, a converging lens forms an image of the same size as the object.
Thus, the image is smaller at a distance of 21cm
Similarly, the image id larger at 19cm
Therefore,
Distance at 20cm = 2f
f = 20/2
= 10
Answer: The focal length of the lens is 10cm
Answer: 10 cm
When object is placed at a distance of 2f from the lens, a converging lens forms an image of the same size as the object.
Thus, the image is smaller at a distance of 21cm
Similarly, the image id larger at 19cm
Therefore,
Distance at 20cm = 2f
f = 20/2
= 10
Answer: The focal length of the lens is 10cm