how does our eye work?

Last week, Jana was trying to explain to Nandu the concept of vision (they came across "eye" in her picture dictionary for body organs), how our eye works when we are trying to see something, how the light rays travel from an object to the eye etc. He used a picture of a ship as an example, and drew the light rays from the ship to the picture of an eye with his finger, and said "this is how you see the ship". She gave this very puzzled expression, and asked, "Why would you put the ship in your eye?". The eye lesson ended quickly after that as it looked like Daddy would have to answer more questions than he was prepared for!