When a beam of white light passes through a glass prism, the colour of light beam that deviates the least is

When white light passes through a glass prism, it undergoes dispersion, separating into its spectral components due to the wavelength-dependent refractive index of the glass [1]. According to Snell's law, the degree of bending or refraction depends on the refractive index of the medium [2]. For most transparent materials like glass, the refractive index increases as the wavelength decreases. Consequently, shorter wavelengths, such as violet and blue light, experience a higher refractive index and are refracted at greater angles, leading to maximum deviation [3]. Conversely, longer wavelengths, specifically red light, encounter a lower refractive index and undergo the smallest amount of bending [3]. Therefore, red light is the color that deviates the least when passing through a prism, while violet light deviates the most [3].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > 10.3 REFRACTION OF LIGHT THROUGH A PRISM > p. 165
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.10 > p. 148
3. [3] https://en.wikipedia.org/wiki/Dispersive_prism