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

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