You are given four sources of light each one providing a light of a single colour-red, blue,green and yellow. Suppose the angle of refraction for a beam of yellow light corresponding to a particular angle of incidence at the interface of two media is `90^@`. Which of the folowing statements is correct it the source of yellow light is replaced with that of other lights without changing the angle of incidence ?

Options

A. The beam of red light would undergo total internal reflection.
B. The beam of red light would bend toward normal while it gets refracted through the second medium.
C. The beam of blue light would undergo total internal reflection.
D. The beam of green light would bend away from the normal as it gets refracted through the second medium.

Explanation

To solve the problem, we need to analyze the situation regarding the refraction of light through different media and how the refractive index affects the behavior of light when the source is changed.

### Step-by-Step Solution:

1. **Understanding the Given Condition**:
- We are given that for yellow light, the angle of refraction (R) is 90 degrees at a certain angle of incidence (I). This implies that the angle of incidence is equal to the critical angle (C) for yellow light.

2. **Critical Angle and Total Internal Reflection**:
- When the angle of refraction is 90 degrees, it indicates that the light is at the critical angle. At this point, any increase in the angle of incidence will result in total internal reflection. The critical angle is defined as:
\[ C = \sin^{-1}\left(\frac{n_2}{n_1}\right) \]
- Here, \( n_1 \) is the refractive index of the medium from which the light is coming, and \( n_2 \) is the refractive index of the medium into which the light is entering.

3. **Refractive Index and Wavelength**:
- The refractive index varies with the wavelength of light. Generally, shorter wavelengths (like blue light) have higher refractive indices compared to longer wavelengths (like yellow light). Therefore, we can conclude that yellow light has a larger critical angle compared to blue light.

4. **Replacing Yellow Light with Other Colors**:
- If we replace yellow light with blue light while keeping the angle of incidence the same, we need to consider the refractive index of blue light. Since blue light has a shorter wavelength, it will have a higher refractive index compared to yellow light.

5. **Analyzing the New Situation**:
- If the angle of incidence remains the same and is greater than the critical angle for blue light, then total internal reflection will occur. Since blue light has a higher refractive index, its critical angle will be smaller than that of yellow light.

6. **Conclusion**:
- Therefore, if yellow light is replaced with blue light, the angle of incidence will be greater than the critical angle for blue light, leading to total internal reflection. Thus, the correct statement is that the beam of blue light will undergo total internal reflection.

### Final Answer:
The correct statement is: **The beam of blue light will undergo total internal reflection.**