1) Thin films, such as soap bubbles or gasoline on water, often have a multi-coloured appearance that sometimes changes while you are watching. Explain the multi-coloured appearance of these films and why their appearance changes with time.

Question

2) Yellow light is incident on a single-slit 0.0315 mm wide. On a screen 70.0 cm away, a dark band appears 13.0 mm from the centre of the bright central band. Calculate the wavelength of the light.

Answer 1

1. is the film the same thickness throughout? (ans NO) What is interference?

2. This is a standard formula.