Discuss the position and nature of the image formed by a concave mirror when the object is moved from infinity towards the pole of the mirror.
As the object is moved from infinity towards the pole of a concave mirror the image shifts from the focus of the mirror to infinity. When the object is at infinity, the image is formed at the principal focus or in the focal plane. As the object is shifted, further the image is formed between the principal focus and centre of curvature, then at the centre of curvature, the beyond the centre of curvature, then at infinity and finally the image is formed behind the mirror. The size of the image goes on increasing.