physics (light)

1.What type of mirror can be used as security mirror, shaving mirror and driving mirror respectively??(concave/convex)and why??

A: security mirror and driving mirror - convex mirror
The image formed by the mirror is always erect which is the primary requirement for used as a security mirror or driving mirror, as inverted images are NOT convenient to the observers or drivers.

Secondly, convex mirror procides a wide field of view, which is suitable for use in the said purposes.
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2.Why the images formed by short sight glasses are diminished when we are not wearing them but at original size of objects when we are wearing them??

A: Short sight glasses are concave lenses. From ray-diagrams, you can be able to see that images formed by a concave lens are always diminished.

When we just look through a pair of short-sight glasses, what we see is the images formed by the glasses which act as ordinary concave lenses.

However, when we are wearing the glasses, the glass and the lens of our eye (which is a convex lens) formed a combined lens system. The dimished image formed by the glass (a concave lens) is magnified by the eye lens (a convex lens) in the same way as what a magifying glass does.