Question

why do soap and petrol give out the seven colours when they are exposed in sunlight

Answer 1

due to refraction

Answer 2

chromatic dispersion takes place

Answer 3

but does it depend on the materialistic properties

Answer 4

yes

Answer 5

its due to dispersion of light.. white light has 7 colours say VIBGYOR.. when white light passes through petrol or soap, different colours get dispersed.. since each colour has its own wavelength n phase velocity, it gets disperse at different angles.. so we can see different colours

Answer 6

This wikipedia article [ http://en.wikipedia.org/wiki/Soap_bubble#Interference_and_reflection ] says that it is due to interference - not refraction and dispersion.