By observing steel vessels and different images in them

By observing steel vessels and different images in them; Surya, a third class
student, asked his elder sister Vidya some questions. What may be those
questions ?

  1. Why do we see our image in some vessels which bulged outwards ?
  2. Why do we not able to see our image in some vessels which bulged inwards ?
  3. Which type of vessels are useful to reflect light on wall and form our image on wall ?
  4. What is the difference between the vessels which bulged inwards and the vessels which bulged outwards ?