$(a)$ The refractive index of diamond is $2.42$. What is the meaning of this statement?
$(b)$ Redraw the diagram given below in your answer book and complete the path of the ray.
$(c)$ What is the difference between virtual images produced by concave and convex mirrors?
$(d)$ What does the negative sign in the value of magnification produced by a mirror indicate about an image?

(N/A) This means that the ratio of the speed of light in air/vacuum to the speed of light in diamond is $2.42$.
$(b)$ The two figures are shown below,completing the path of the light rays.
$(c)$ $A$ virtual image produced by a concave mirror is magnified,whereas a virtual image produced by a convex mirror is always diminished. $A$ virtual image produced by a plane mirror is of the same size as the object.
$(d)$ The negative sign in the magnification value indicates that the image formed is real and inverted.