It is a common observation that some people use spectacles for reading. The watch repairer uses a small magnifying glass to see tiny parts of a watch.
• Have you ever touched a magnifying glass with your hand?
• Have you touched the glass in the spectacles used for reading with your hand?
• Is it a plane or curved surface?
• Is it thicker in the middle or at the edge?

We have learnt about refraction of light at a plane surface in the previous chapter. Now let us understand refraction of light at curved surfaces.
Let us do an activity to understand refraction of light at curved surfaces.

Refraction of light at a curved surface

Draw an arrow of length 4 cm using a black sketch pen on a thick sheet of paper. Take an empty cylindrical-shaped transparent vessel such as glass tumbler. Keep it on the table. Ask your friend to bring that sheet of paper on which arrow was drawn behind the vessel while you looking at it from the other side (The arrow mark should be in horizontal position).