A ray travelling parallel to the optical boundary along its surface

Options

A. will undergo no refraction
B. will partially refract and partially travel undeviated
C. will suffer total internal reflection
D. none of the above

Explanation

**Step-by-Step Solution:**

1. **Understanding the Scenario**: We have a ray of light traveling parallel to the optical boundary between two different media. Let's denote the refractive index of the medium on the left side of the boundary as \( n_1 \) and the refractive index on the right side as \( n_2 \).

2. **Analyzing the Ray's Path**: Since the ray is traveling parallel to the optical boundary, it means that it is not entering the second medium at an angle but rather is aligned with the boundary itself.

3. **Refraction Principles**: According to the principles of refraction, when light travels from one medium to another, it can either refract (change direction) or reflect (bounce back). The behavior of the light ray depends on the angle of incidence and the refractive indices of the two media.

4. **Applying Snell's Law**: Snell's Law states that \( n_1 \sin(\theta_1) = n_2 \sin(\theta_2) \). In this case, since the ray is parallel to the boundary, the angle of incidence \( \theta_1 \) is 0 degrees. Therefore, \( \sin(0) = 0 \), which means that the angle of refraction \( \theta_2 \) will also be 0 degrees.

5. **Conclusion on Refraction**: Since the ray does not change direction (it continues to travel parallel to the boundary), we conclude that the ray will not undergo any refraction.

6. **Selecting the Correct Option**: Based on the analysis, the correct answer to the question is that the ray will undergo no refraction.

**Final Answer**: The ray traveling parallel to the optical boundary will undergo no refraction.

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