Which type of image cannot be obtained by a concave mirror?

You are given water,mustard oil,glycerine,and kerosene. In which of these media would a ray of light incident obliquely at the same angle bend the most?

The ray diagram given below illustrates the experimental setup for the determination of the focal length of a converging lens using a plane mirror.
$(i)$ State the magnification of the image formed.
$(ii)$ Write two characteristics of the image formed.
$(iii)$ What is the name given to the distance between the object and the optical centre of the lens in the given diagram?

$(a)$ Write any three differences between concave and convex mirror.
$(b)$ Draw ray diagram to show what happens to a ray of light after reflection from a convex mirror,if it
$(i)$ is incident parallel to principal axis.
$(ii)$ incident at the pole.

Where does an object and its image coincide in a concave mirror?

An object,$4.0 \, cm$ in size,is placed $25.0 \, cm$ in front of a concave mirror of focal length $15.0 \, cm$. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image.