<P> When light shines onto a bubble it appears to change colour . Unlike those seen in a rainbow , which arise from differential refraction , the colours seen in a soap bubble arise from interference of light reflecting off the front and back surfaces of the thin soap film . Depending on the thickness of the film , different colours interfere constructively and destructively . </P>
colours seen in soap bubbles are due to
interference of light reflecting off the front and back surfaces of the thin soap film