ooject 2 cm tall is kept on the principal axis of a converging lens of focal length
cm. Find the position, nature and size of the image formed if the object is at 12
from the lens. Also find the magnfication produced by the lens.
• height of the nhiert h - ? om
Answers
Explanation:
Converging lens is a convex lens
Given:
Focal length (f) = +8 cm
Height of the object (h) = +2
(a)
(i) Object distance (u) =-2
Lens formula is given as:
1/f=1/v-1/u
v=24cm
Image is at a distance of 24 cm from the convex lens; therefore, we have:
Magnification =v/u
=24/-12
= -2
Hence, the image is real and inverted.
(b) Object distance (u)=-6
According to lens formula:
v=24
Image is at a distance of 24 cm in front of the lens; therefore , we have :
m=v/u
m=-24/-6
m=4
m=Hí/H•
Hí= 8cm
Height of the image is 8 cm.
Here, height is positive; therefore, image is virtual and erect.
The practical application for case (1) is that it can be used as a corrective lens for a farsighted person and for case (2), it can be used as a magnifying lens for reading purposes.