Which phenomenon cannot be attributed to refraction of light?

Red Shift is a phenomenon related to the Doppler Effect — it occurs when a light source moves away from the observer, causing the wavelength of light to stretch and shift toward the red end of the spectrum. This has absolutely nothing to do with the bending of light through different media, which is what refraction is all about. Every student must clearly remember that Red Shift is used by astronomers to measure how fast galaxies are moving away from Earth — it is a concept from astrophysics, not optics.

• Red Shift: Caused by Doppler Effect when a light-emitting object moves away from observer — wavelength increases, shifting light toward red end of spectrum
• Twinkling of Stars: Caused by atmospheric refraction — starlight bends as it passes through different layers of atmosphere with varying densities
• Mirage: Caused by total internal reflection — light continuously refracts through progressively hotter air layers near the ground until it bends back upward, creating an illusion of water on the surface
• Rainbow: Caused by dispersion of sunlight through water droplets — involves refraction, internal reflection, and dispersion of white light into seven colours