A ray of light containing both red and blue colours is incident on the refracting surface of a prism. Then.

Options

A. both colours suffer equal deviation
B. red colour suffers more deviation
C. red colour suffers less.deviation
D. deviation depends on the angle of prism

Answer

To solve the problem, we need to analyze how different colors of light behave when they pass through a prism. The key points to consider are the relationship between the wavelength of light, the refractive index, and the deviation of light.

### Step-by-Step Solution:

1. **Understanding the Problem**:
We have a ray of light that contains both red and blue colors incident on a prism. We need to determine how each color is affected in terms of deviation when passing through the prism.

2. **Refractive Index and Wavelength**:
According to Cauchy's relation, the refractive index (μ) of a material is inversely proportional to the square of the wavelength (λ) of light:
\[ \mu = \frac{a + b}{\lambda^2} \]
Here, \(a\) and \(b\) are constants. This implies that as the wavelength increases, the refractive index decreases.

3. **Comparing Wavelengths**:
The wavelength of red light is longer than that of blue light. Therefore, we can conclude:
\[ \lambda_{\text{red}} > \lambda_{\text{blue}} \]
This means that:
\[ \mu_{\text{red}} < \mu_{\text{blue}} \]
The refractive index of red light is less than that of blue light.

4. **Deviation and Refractive Index**:
The deviation of light in a prism is directly related to the refractive index. A higher refractive index results in greater deviation. Since we have established that the refractive index of red light is less than that of blue light, we can conclude:
\[ \text{Deviation of red} < \text{Deviation of blue} \]

5. **Conclusion**:
From the above analysis, we can determine that the red color suffers less deviation than the blue color when passing through the prism. Therefore, the correct answer is:
- **Red color suffers less deviation**.

### Final Answer:
**Red color suffers less deviation.**

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