An object is placed at a distance of 15 cm from a convex lens of focal length 20 cm. List four characteristics (nature, position, etc.) of the image formed by the lens.

Given that u = -15 cm (object distance, negative sign indicates object is placed in front of the lens)
f = 20 cm (focal length, positive for convex lens)

Now, By lens formula
1/f = 1/v - 1/u
1/v = 1/f + 1/u
1/v = 1/20 + 1/(-15)
1/v = (3 - 4) / 60
1/v = -1/60
=> v = -60 cm

The image is formed at 60 cm to the left of the lens (negative sign indicates virtual image).
Since v is negative, the image is virtual.
Since the magnification, M = -v/u = -(-60)/(-15) = -4, the image is inverted.
Since |M| >1 the image is magnified.
Therefore, the characteristics of the image are:

1. Virtual
2. Inverted
3. Magnified
4. Formed at 60 cm to the left of the lens