The correct answer is option 1: refractive index of glass for different colors of light is different.
When white light passes through a glass prism, it undergoes dispersion, which is the splitting of light into its different component colors. This occurs because the refractive index of glass varies with the wavelength or color of light. The refractive index of a material determines how much the speed of light changes when it passes through the material. Different colors of light have different wavelengths, so they are affected differently by the glass prism.
The refractive index of glass is higher for shorter-wavelength colors, such as violet and blue, compared to longer-wavelength colors, such as red and orange. This means that the speed of these shorter-wavelength colors decreases more when passing through the glass prism, causing them to bend or refract more than the longer-wavelength colors. As a result, the white light is spread out into a spectrum of colors, known as a rainbow or a visible spectrum.
Therefore, it is the difference in the refractive index of the glass for different colors of light that causes white light to break up into its component colors when passing through a glass prism.