The rainbow-like colours seen when a CD is viewed in sunlight are caused by the reflection of light off the finely spaced tracks of pits and lands on the disc surface. These tracks act as a diffraction grating. When white light is reflected and passes over these tiny structures, it is diffracted, meaning it bends and splits into its constituent wavelengths (colours) at slightly different angles, creating the spectrum effect.
When a CD (compact disc used in audio and video systems) is seen in sunlight, rainbow like colours are seen. This can be explained on the basis of the phenomenon of :
Asked in HPPSC HPAS Prelims 2014 · UPPCS Prelims 2000 · Topic: Optics (Diffraction: Fraunhofer and Fresnel diffraction, diffraction grating)
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