Exhibit: Bubble Film Projector
When the frame is dipped into the detergent solution and released, a thin film is left across the circular opening. Because the film of liquid is vertical, it begins to run down, as such, the film gets thinner and thinner at the top (and thicker at the bottom) until it bursts. The colours on the film gradually move downwards – the projector inverts the picture, so the colours on the screen move upwards.
The colours occur because white light is made up of a whole rainbow of different colours, and only some of these colours are reflected by a film of any given thickness. As the thickness changes, the colour of the reflected light changes.