Magnification is the ratio of which of the following?

Discuss the position and nature of the image formed by a concave mirror when the object is moved from infinity towards the pole of the mirror.

$A$ student focused the image of a candle flame on a white screen using a convex lens. He noted down the positions of the candle,screen,and lens as follows:
Position of candle $= 12.0 \, cm$
Position of convex lens $= 50.0 \, cm$
Position of the screen $= 88.0 \, cm$
$(i)$ What is the focal length of the convex lens?
$(ii)$ Where will the image be formed if he shifts the candle towards the lens to a position of $31.0 \, cm$?

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.

If a convex lens forms a real and magnified image of an object,where is the object placed?

Write down four important characteristics of the image formed by a plane mirror.