Activity . Draw a thick straight line in ink, over a sheet of white paper placed on a Table. Place a glass slab over the line in such a way that one of its edges makes an angle with the line. Look at the portion of the line under the slab from the sides.
What do you observe? Does the line under the glass slab appear to be bent at the edges? Next, place the glass slab such that it is normal to the line. What do you observe now?
Does the part of the line under the glass slab appear bent? Look at the line from the top of the glass slab. Does the part of the line, beneath the slab, appear to be raised? Why does this happen?