Which one of the following phenomena cannot be attributed to the refraction of light?

Refraction is the bending of light as it passes through media of different densities or refractive indices. The twinkling of stars is caused by atmospheric refraction, where starlight undergoes continuous bending due to the Earth's varying atmospheric layers [1][t1]. Mirages are also a result of atmospheric refraction near the ground, where temperature gradients cause light to deviate from a straight line [t2][t7]. Rainbows involve a combination of refraction, reflection, and dispersion as sunlight enters and exits water droplets [t6][t8]. In contrast, Red shift is an astronomical phenomenon where the wavelength of light increases (shifting toward the red end of the spectrum) because the source is moving away from the observer [c3]. This is attributed to the Doppler effect or the expansion of the universe, rather than the bending of light through a medium [t3].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > Twinkling of stars > p. 168