Choose the incorrect statement for the polarisation by reflection.

Options

A. The reflected light and refracted light is at `90^0` in complete polarization by reflection
B. If `theta_p`, is angle of polarization, then refractive index should always be greater than tan `theta_p`
C. At the angle of polarization, the percentage of the polarized light in the reflected beam is greatest
D. Both (1) & (3)

Answer

To solve the question of identifying the incorrect statement regarding polarization by reflection, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Polarization by Reflection**:
- When unpolarized light strikes a surface, part of it is reflected and part of it is refracted. At a certain angle of incidence, known as the angle of polarization (θp), the reflected light becomes plane polarized.

2. **Analyzing Option 1**:
- Option 1 states that reflected light is at 90 degrees in complete polarization by reflection.
- This is true because at the angle of polarization, the reflected light is indeed plane polarized, and the angle between the reflected and refracted rays is 90 degrees.
- **Conclusion**: This statement is correct.

3. **Analyzing Option 2**:
- Option 2 refers to Brewster's Law, stating that if θp is the angle of polarization, then the refractive index (n) is equal to tan(θp).
- The statement claims that the refractive index is greater than tan(θp), which is incorrect. According to Brewster's Law, n = tan(θp).
- **Conclusion**: This statement is incorrect.

4. **Analyzing Option 3**:
- Option 3 states that at the angle of polarization, the percentage of polarized light in the reflected beam is greater.
- This is true because at the angle of polarization, the reflected light is maximally polarized, meaning a higher percentage of the reflected light is polarized compared to light reflected at other angles.
- **Conclusion**: This statement is correct.

5. **Final Conclusion**:
- Since Option 2 is the only incorrect statement regarding polarization by reflection, it is the answer to the question.