When viewed in white light, a soap bubble shows colours because of
Dispersion
Interference
Scattering
Diffraction
Due to interference, when soap bubble is viewed in white light it shows colours.
Dispersion of white light occurs because different colours of white light undergo different extents of refraction. The dispersion is not evident in a glass slab like it is evident in a prism because the two refracting surfaces are parallel to each other.