For a total internal reflection, which of the following is correct ?

Options

A. Light travel from rarer to denser medium.
B. Light travel from denser to rarer medium.
C. Light travels in air only.
D. Light travels in water only.

Explanation

To determine the correct statement regarding total internal reflection, we need to understand the concept and conditions under which total internal reflection occurs. Here is a step-by-step solution:

### Step-by-Step Solution:

1. **Understanding Total Internal Reflection**:
- Total internal reflection is a phenomenon that occurs when a light ray travels from a denser medium to a rarer medium and is completely reflected back into the denser medium.

2. **Identifying the Mediums**:
- A denser medium has a higher refractive index (e.g., water, glass), while a rarer medium has a lower refractive index (e.g., air).

3. **Conditions for Total Internal Reflection**:
- Total internal reflection occurs only when the light is traveling from a denser medium to a rarer medium. If the light travels from a rarer medium to a denser medium, refraction occurs instead of reflection.

4. **Analyzing the Options**:
- **Option 1**: Light travels from rarer medium to denser medium - This is incorrect for total internal reflection.
- **Option 2**: Light travels from denser medium to rarer medium - This is correct and aligns with the definition of total internal reflection.
- **Option 3**: Light travels in air only - This is incorrect because total internal reflection requires a denser medium to start with.
- **Option 4**: Light travels in water only - This is also incorrect because total internal reflection involves the transition from water (denser) to air (rarer), not just water.

5. **Conclusion**:
- The correct statement regarding total internal reflection is that "light travels from denser medium to rarer medium."

### Final Answer:
The correct option is: **Light travels from denser medium to rarer medium.**

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