Question

what do you mean by magnification less than unity?

Answer 1

Image is diminished ie size of image is less than the size of object

Answer 2

Magnification is the process of enlarging the appearance, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in size, sometimes called "minification" or "de-magnification . Magnification less than unity means size of the image is smaller than object.

hope it helps you....