I have doubts in the following questions.Please explain them to me Sir.

1.An object is held at 30cm in front of a convex mirror of focal length 15cm.At what distance from the convex mirror a plane mirror be held so that the images coincide with each other?

2.What is the value of focal length of a plane mirror?

3.How can you distinguish between a plane,concave and convex mirror without touching them?

4.It is desired to obtain an erect image of an object,using a concave mirror of focal length 20cm.

 What should be the range of distance of the object from the mirror?

5.A ray of light is deviated through an angle of 60' by a plane mirror.Find

  a)incident angle.

  b)reflected angle.

  c)angle between the mirror and the direction of incident ray.