Ordinary light is incident on the upper surface of a glass slab at theh polarizing angle. Then

Options

A. the reflected ray is completely plane polarized with vibrations perpendicular to the plane of incidence
B. the refracted ray is also completely plane polarized with vibrations in the plane of incidence
C. the reflected ray is partically polarized with vibrations perpendicular to the plane of incidence
D. both reflected and refracted rays are completely polarized having both of them vibrations in the plane of incidence

Answer

To solve the problem regarding ordinary light incident on the upper surface of a glass slab at the polarizing angle, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the Polarizing Angle**:
The polarizing angle (also known as Brewster's angle) is defined as the angle of incidence at which light reflected from a surface is completely polarized. This occurs when the reflected and refracted rays are perpendicular to each other.

2. **Identify the Angle**:
Let’s denote the polarizing angle as θ_p. According to Brewster's law, this angle is given by:
\[ \tan(\theta_p) = \frac{n_2}{n_1} \]
where \( n_1 \) is the refractive index of the first medium (air, typically taken as 1) and \( n_2 \) is the refractive index of the second medium (glass).

3. **Incident Light**:
When ordinary light (which is unpolarized) strikes the glass slab at the polarizing angle \( \theta_p \), it can be divided into two components: the reflected ray and the refracted ray.

4. **Behavior of the Reflected Ray**:
At the polarizing angle, the reflected ray becomes completely plane polarized. This means that all the light waves in the reflected ray vibrate in a single plane, which is perpendicular to the plane of incidence.

5. **Behavior of the Refracted Ray**:
The refracted ray will continue into the glass slab, but it will not be polarized. The vibrations of the light waves in the refracted ray will be in multiple planes.

6. **Conclusion**:
Therefore, when ordinary light is incident on the upper surface of a glass slab at the polarizing angle, the reflected ray is completely plane polarized, and the refracted ray is not polarized.

### Final Answer:
When ordinary light is incident on the upper surface of a glass slab at the polarizing angle, the reflected rays are completely plane polarized, and the refracted rays are not polarized.

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