Question

if the object is at focus then what is the nature and position of the image​

Answer 1

Answer:

No image will be seen. The object and the image will be at the same place. Concave mirror converges all rays of light at the focus. In case of object placed at focus the rays of light reflected from the surface of object will be diverging in nature. These rays will be incident on the surface of concave mirror, get reflected and converge at the focus. Since object is already at focus the image will be on the focus but not visible.

Reasons(that i can list) for not seeing the image:

If object is not a light emitting source, the light reflected from surface (let’s say s1) and the light reflected from mirror (let’s say s2). Intensity of s1 will be always greater than s2. Lower intensity hence not visible.

If the object is a light emitting source, the place where the image is formed is already having the same type of rays except for intensity. The intensity of source will always be greater.