Prism Deviation Least Color Explained

When white light enters a glass prism, it undergoes dispersion, splitting into its constituent colors (like in a rainbow). This happens because the prism material affects different colors (wavelengths) of light slightly differently.

The spectrum of visible light consists of colors from Violet to Red. The order is typically remembered as VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red).

Understanding Light Deviation and Wavelength

The key principle governing this phenomenon is the relationship between the wavelength of light, the refractive index of the prism material, and the angle of deviation:

• Wavelength ($\lambda$): Light travels as waves. Different colors have different wavelengths. Violet light has the shortest wavelength, while red light has the longest wavelength within the visible spectrum.
• Refractive Index ($n$): This measures how much light slows down and bends when entering a material. For glass, the refractive index is not constant for all colors. It generally follows the trend where shorter wavelengths (like violet) have a higher refractive index, and longer wavelengths (like red) have a lower refractive index. This relationship can be approximated by formulas like Cauchy's equation, where $n$ decreases as $\lambda$ increases.
• Angle of Deviation ($\delta$): This is the angle between the incoming light ray and the outgoing light ray after passing through the prism. The greater the refractive index ($n$) for a specific color, the greater its angle of deviation ($\delta$).

Color Deviation Comparison

Applying these principles:

• Violet light, having the shortest wavelength ($\lambda$), encounters the highest refractive index ($n$) in glass. Consequently, it bends the most, resulting in the largest angle of deviation ($\delta$).
• Red light, possessing the longest wavelength ($\lambda$), experiences the lowest refractive index ($n$) in glass. As a result, it bends the least, leading to the smallest angle of deviation ($\delta$).
• The other colors (Orange, Yellow, Green, Blue, Indigo) fall in between, with their deviation increasing from red to violet.

Summary of Prism Effects

Based on this, the color that experiences the minimum bending or least deviation when passing through a glass prism is Red.