Answer:
1) Some light waves bounce off the inner part of the film.
2) In doing so they travel a bit than the waves bouncing off the outer waves.
so we see colors repeat in pattern in a thin soap film
Step-by-step explanation:
A colorful interference pattern is observed when light is reflected from the top and bottom boundaries of a thin oil film. The different bands form as the film's thickness diminishes from a central runoff-point.
When white light shines on a bubble, strange things happen. When light waves hit a bubble, some of them bounce straight back off the outer part of the soap film. Others carry on through but then bounce off the inner part of the film. So one set of light rays shine into a soap bubble, but two sets of rays come back out again. When they emerge, the waves that bounce off the inner film have traveled a tiny bit further than the waves that bounced off the outer film. So we have two sets of light waves that are now slightly out of step. Like two sets of ripples on a pond, these waves start merging. Just like on a pond, some add together and some cancel out. The overall effect is that some of the colors in the original white light disappear altogether, leaving other colors behind. These are the colors you see in soap bubbles.