Explanation:

- Diffraction of the Light: This is the correct explanation. A CD or DVD has closely spaced tracks that act as a diffraction grating, causing light to spread out into a spectrum and produce a rainbow effect.

- Thin-Film Interference of the light: Although it also produces colorful effects through interference, it is not the cause of the rainbow pattern on CDs or DVDs.

- Scattering of the light: This involves light being dispersed in different directions and does not cause the rainbow pattern observed.

- Polarisation of the light: This refers to the orientation of vibrations of light waves and is unrelated to the rainbow effect on these discs.