Refraction through a Glass Slab
To see refraction through a rectangular slab.
Rectangular glass slab, pencil, scale, sheet of paper, laser torch
Draw a thick, long line on sheet of paper. Place a transparent rectangular glass or plastic slab on the line in such a way that the longer edges of the slab makes an angle of about 45 degree. with the line.
From different positions, look at the line through the slab. First look at it vertically from the top. The line below the slab will appear raised. Now look along the line from one side of the slab, with your eyes about the same level as slab. The line on the other side of the slab will appear displaced. This happens because the rays from the line get shifted sideways on passing through the slab.
Try to see path of the ray through glass slab by using a laser torch.