Which of the following colours of light undergoes the least deviation while passing through a glass prism?

Options

A. Red
B. Blue
C. Yellow
D. Green

Answer

To determine which color of light undergoes the least deviation while passing through a glass prism, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Refraction**: Refraction occurs when light passes from one medium to another, such as from air to glass. The degree of bending or deviation of light depends on the wavelength of the light and the refractive index of the medium.

2. **Spectrum of Light**: The visible spectrum consists of seven colors: red, orange, yellow, green, blue, indigo, and violet. These colors can be arranged in order of increasing wavelength: red has the longest wavelength, and violet has the shortest.

3. **Refractive Index and Wavelength**: The refractive index (n) of a medium is inversely proportional to the wavelength (λ) of light. This means that as the wavelength increases, the refractive index decreases. Conversely, shorter wavelengths (like violet) have a higher refractive index.

4. **Deviation of Colors**: When light passes through a prism, different colors bend by different amounts due to their varying refractive indices. The color with the lowest refractive index will undergo the least deviation, while the color with the highest refractive index will undergo the most deviation.

5. **Identifying the Color with Least Deviation**: Since red light has the longest wavelength, it has the lowest refractive index among the visible spectrum. Therefore, red light will undergo the least deviation when passing through a glass prism.

6. **Conclusion**: The color of light that undergoes the least deviation while passing through a glass prism is **red light**.

### Final Answer:
Red light undergoes the least deviation while passing through a glass prism.

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