Dispersion process forms spectrum, due to white light falling on a prism. The light wave with shortest wavelength :

Dispersion occurs because the refractive index of a material like glass depends on the wavelength of the incident light [3]. According to Snell's law, the degree of bending or refraction is determined by this refractive index [1]. In most transparent media, the refractive index increases as the wavelength decreases. Consequently, light waves with shorter wavelengths, such as violet, travel more slowly through the prism and experience a greater change in direction compared to longer wavelengths like red. This results in shorter wavelengths refracting the most at both the entry and exit interfaces of the prism. While red light (longest wavelength) undergoes the least deviation, violet light (shortest wavelength) is deflected at the greatest angle, leading to the separation of white light into its constituent spectral colors [3].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.10 > p. 148
2. [3] https://en.wikipedia.org/wiki/Dispersive_prism