What is the radius of curvature of a plane mirror?

$(a)$ 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?

What type of mirror is used to obtain a real image?

What is the power of a plane glass sheet?

State Snell's law of refraction.

Does the magnification equation change depending on whether the lens is a concave lens or a convex lens?