Through which point of a convex lens does a ray of light pass without undergoing refraction?

State the sign convention for lenses regarding object and image distances.

The magnification of a real image formed by a concave mirror is always ...

Name two spherical mirrors. Define them. Write any three points of difference between them.

State the laws of refraction. Explain the phenomenon of refraction when a ray of light passes through a rectangular glass slab with the help of a ray diagram.

Draw the ray diagram in each case to show the position,nature,and size of the image formed when the object is placed:
$(i)$ At the centre of curvature of a concave mirror.
$(ii)$ Within the focal length of a convex lens.
$(iii)$ Between the pole and focus of a concave mirror.
$(iv)$ In front of a convex mirror.
$(v)$ In front of a concave lens.