Look through the window. You will see the picture of a dragon. Now rotate the disc of the window slowly while you are looking through it. Observe that its colour is changing. The picture of the dragon is made of pieces of transparent adhesive tape and is placed between two polarising films – one at the back of the picture through which light falls on it and the other, inside the disc through which you are looking. When polarised light falls on the picture, the pieces of adhesive tape, being optically active, rotate the plane of polarisation of light. The front polarising film allows lights of particular colours to come through it and as a result, we see a pattern of changing colours as the disc is rotated. Look through the small hole without any polariser.