An object placed in front of the convex lens at a distance of 25cm on the principal axis.  The focal length of lens is 15cm, at what distance the image is formed and writes the nature and size of the image.


Asked by craj.fru | 2nd Sep, 2019, 09:45: AM

Expert Answer:

We have lens equation :   (1/v) - (1/u) = 1/f  ..............................(1)
where v is lens-to-image distance, u is lens-to-object distance and f is focal length
By sign convention, u is -ve.
hence from eqn.(1), we get,  1/v = (1/15) - (1/25)    or v = 37.5 cm
magnification m = v/u = 37.5/(-25) = -1.5
Hence image is formed on other side of lens at a distance 37.5 cm from lens.
Image is magnified by 1.5 times. image is real and inverted.

Answered by Thiyagarajan K | 2nd Sep, 2019, 10:31: AM