convex mirrors form diminished images so such mirrors are useful in car rear views to have a better view of the traffic behind
It looks like the mirrors do not unbolt for the brackets, the set i have unbolts from the bottom with a 13 mm nut, there a washer, spring and a 2nd washers, if there's no bolt under your bracket you'll need a set of mirrors, there may be a cap coveri...
Because they are convex mirrors to give you a wider field of vision. The convex shape make objects appear farther away.