When unpolarised light beam is incident from air onto glass (`n=1.5`) at the polarising angle

Options

A. reflected beam is polarised 100 percent
B. reflected and refracted beams are partially polarised
C. the reason for (1) is that almost all the light is refelcted
D. all of the above

Answer

To solve the problem of unpolarized light incident from air onto glass at the polarizing angle, we can follow these steps:

### Step 1: Understand the Concept of Polarizing Angle
The polarizing angle (also known as Brewster's angle) is the angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection.

### Step 2: Use Brewster's Law
Brewster's Law states that the polarizing angle (θ_p) is related to the refractive indices of the two media. The formula is given by:
\[ \tan(\theta_p) = \frac{n_2}{n_1} \]
where \( n_1 \) is the refractive index of the first medium (air, \( n_1 \approx 1 \)) and \( n_2 \) is the refractive index of the second medium (glass, \( n_2 = 1.5 \)).

### Step 3: Calculate the Polarizing Angle
Substituting the values into Brewster's Law:
\[ \tan(\theta_p) = \frac{1.5}{1} = 1.5 \]
Now, we can find the angle \( \theta_p \):
\[ \theta_p = \tan^{-1}(1.5) \]
Using a calculator, we find:
\[ \theta_p \approx 56.31^\circ \]

### Step 4: Conclusion
At the polarizing angle of approximately \( 56.31^\circ \), the reflected light is completely plane polarized.

### Final Answer
The polarizing angle when unpolarized light beam is incident from air onto glass (n=1.5) is approximately \( 56.31^\circ \).

---