问题

You are supposed to provide a solution to a given problem.

Problem:
Malus' law: $I=I_0*cos^2($\theta$)$. Where I is the intensity of polarized light that has passed through the polarizer, I_0 is the intensity of polarized light before the polarizer, and $\theta$ is the angle between the polarized light and the polarizer. Unpolarized light passes through a polarizer. It then passes through another polarizer at angle 40 degree to the first, and then another at angle 15 degree to the second. What percentage of the original intensity was the light coming out of the second polarizer?
Solution:

答案

模型 模型答案 正确答案
金声玉亮2.0 Let's denote the original intensity of the unpolarized light as $I_0$. When unpolarized light passes through a polarizer, it becomes polarized, and its intensity is halved (since only half of the light is polarized in the direction of the polarizer). Let's call the intensity after the first polarizer $I_1$. According to Malus' law, $I_1 = \frac{1}{2}I_0$.

The light then passes through a second polarizer at an angle of 40 degrees to the first. The intensity of the light after the second polarizer, which we'll call $I_2$, can be found using Malus' law again:

$$I_2 = I_1 \cos^2(40^\circ) = \frac{1}{2}I_0 \cos^2(40^\circ)$$

Plugging in the value for $\cos(40^\circ)$:

$$I_2 = \frac{1}{2}I_0 (0.7660444431)^2 \approx \frac{1}{2}I_0 (0.58657) \approx 0.293285 I_0$$

Therefore, the percentage of the original intensity that was the light coming out of the second polarizer is approximately 29.33%.
54.8
deepseekr1

The percentage of the original intensity after the second polarizer is calculated as follows:

1. **First Polarizer (Unpolarized to Polarized):**
Unpolarized light passing through a polarizer reduces its intensity by half:
\[
I_1 = \frac{1}{2} I_0
\]

2. **Second Polarizer (40° Angle):**
Applying Malus' law for polarized light at an angle of 40°:
\[
I_2 = I_1 \cos^2(40^\circ) = \frac{1}{2} I_0 \cos^2(40^\circ)
\]

3. **Calculation:**
- \(\cos(40^\circ) \approx 0.7660\)
- \(\cos^2(40^\circ) \approx 0.5868\)
- Multiply by \(\frac{1}{2}\):
\[
\frac{1}{2} \times 0.5868 = 0.2934
\]
- Convert to percentage:
\[
0.2934 \times 100\% \approx 29.3\%
\]

**Final Answer:**
\boxed{29.3\%}
54.8
gpto1 To solve this problem, we'll use Malus' Law and understand how polarizers affect the intensity of light.

**Step 1: Unpolarized Light Passing Through the First Polarizer**

When unpolarized light passes through a polarizer, the intensity of the transmitted light is reduced by half. This is because the polarizer only allows the component of light polarized along its axis to pass through.

\[
I_1 = \frac{1}{2} I_0
\]

where:
- \( I_0 \) is the original intensity of the unpolarized light.
- \( I_1 \) is the intensity after the first polarizer.

**Step 2: Light Passing Through the Second Polarizer**

The light exiting the first polarizer is now polarized along its axis. When this polarized light passes through a second polarizer at an angle \( \theta_1 = 40^\circ \) relative to the first, Malus' Law applies:

\[
I_2 = I_1 \cos^2 \theta_1
\]

Substituting \( I_1 \):

\[
I_2 = \left( \frac{1}{2} I_0 \right) \cos^2 40^\circ
\]

**Calculating \( \cos^2 40^\circ \):**

\[
\cos 40^\circ \approx 0.7660
\]
\[
\cos^2 40^\circ = (0.7660)^2 \approx 0.5868
\]

**Step 3: Compute the Intensity After the Second Polarizer**

\[
I_2 = \left( \frac{1}{2} I_0 \right) \times 0.5868
\]
\[
I_2 = 0.2934 \, I_0
\]

**Step 4: Calculate the Percentage of the Original Intensity**

\[
\text{Percentage} = \left( \frac{I_2}{I_0} \right) \times 100\%
\]
\[
\text{Percentage} = (0.2934) \times 100\% \approx 29.34\%
\]

**Answer:**

Approximately 29% of the original intensity comes out of the second polarizer.
54.8
GPT-4o To solve this problem, we need to apply Malus' Law multiple times, as the light passes through multiple polarizers.

### Step 1: Unpolarized Light through the First Polarizer

When unpolarized light passes through a polarizer, the intensity of the transmitted light is reduced by half. Therefore, if the initial intensity of the unpolarized light is \(I_0\), the intensity after the first polarizer (\(I_1\)) will be:

\[ I_1 = \frac{I_0}{2} \]

### Step 2: Light through the Second Polarizer

The light coming out of the first polarizer is now polarized. When this polarized light passes through the second polarizer, we use Malus' Law:

\[ I_2 = I_1 \cos^2(\theta_1) \]

where \( \theta_1 \) is the angle between the light's polarization direction (after the first polarizer) and the axis of the second polarizer. Given \( \theta_1 = 40^\circ \):

\[ I_2 = \frac{I_0}{2} \cos^2(40^\circ) \]

### Step 3: Light through the Third Polarizer

Similarly, when the light from the second polarizer passes through the third polarizer, we again use Malus' Law:

\[ I_3 = I_2 \cos^2(\theta_2) \]

where \( \theta_2 \) is the angle between the light's polarization direction (after the second polarizer) and the axis of the third polarizer. Given \( \theta_2 = 15^\circ \):

\[ I_3 = \left( \frac{I_0}{2} \cos^2(40^\circ) \right) \cos^2(15^\circ) \]

### Combining the Results

Now we combine the results to find the intensity \( I_3 \):

\[ I_3 = \frac{I_0}{2} \cos^2(40^\circ) \cos^2(15^\circ) \]

### Numerical Calculation

To find the numerical value, we need to evaluate the cosine terms:

- \( \cos(40^\circ) \approx 0.7660 \)
- \( \cos(15^\circ) \approx 0.9659 \)

Then, we calculate:

\[ \cos^2(40^\circ) \approx (0.7660)^2 \approx 0.5868 \]
\[ \cos^2(15^\circ) \approx (0.9659)^2 \approx 0.9330 \]

Now, calculate the final intensity:

\[ I_3 = \frac{I_0}{2} \times 0.5868 \times 0.9330 \]
\[ I_3 = \frac{I_0}{2} \times 0.5474 \]
\[ I_3 \approx 0.2737 I_0 \]

### Percentage of the Original Intensity

To express \( I_3 \) as a percentage of the original intensity \( I_0 \):

\[ \frac{I_3}{I_0} \times 100\% = 0.2737 \times 100\% \approx 27.37\% \]

Therefore, the light coming out of the second polarizer is approximately **27.37%** of the original unpolarized light intensity.
54.8
llama3.1-70B-Instruct

A nice optics problem!

Let's break it down step by step:

1. Unpolarized light passes through the first polarizer. Since the light is unpolarized, the intensity after the first polarizer is half of the original intensity, i.e., $I_1 = \frac{1}{2}I_0$.
2. The light then passes through the second polarizer, which is at an angle of 40° to the first polarizer. We can apply Malus' law to find the intensity after the second polarizer:

$$I_2 = I_1 \cos^2(40°) = \frac{1}{2}I_0 \cos^2(40°)$$

Using a calculator, we find that $\cos^2(40°) \approx 0.766$.

So, $I_2 \approx \frac{1}{2}I_0 \times 0.766 = 0.383I_0$.

3. The light then passes through the third polarizer, which is at an angle of 15° to the second polarizer. Again, we apply Malus' law:

$$I_3 = I_2 \cos^2(15°) = 0.383I_0 \cos^2(15°)$$

Using a calculator, we find that $\cos^2(15°) \approx 0.933$.

So, $I_3 \approx 0.383I_0 \times 0.933 = 0.358I_0$.

To find the percentage of the original intensity, we divide $I_3$ by $I_0$ and multiply by 100:

$$\frac{I_3}{I_0} \times 100\% \approx \frac{0.358I_0}{I_0} \times 100\% = 35.8\%$$

Therefore, the light coming out of the second polarizer has an intensity of approximately 35.8% of the original intensity.
54.8
llama3.1-405B-Instruct

To find the percentage of the original intensity of the light coming out of the second polarizer, we need to apply Malus' law twice, once for each polarizer.

1. First polarizer:
The light is initially unpolarized, so the intensity after passing through the first polarizer is half of the original intensity, as the polarizer only allows light of one polarization to pass through. Therefore, the intensity after the first polarizer is:

I1 = (1/2) \* I0

2. Second polarizer:
The angle between the first and second polarizers is 40 degrees. Applying Malus' law, we get:

I2 = I1 \* cos^2(40°)

Substituting the value of I1, we get:

I2 = (1/2) \* I0 \* cos^2(40°)

3. Third polarizer:
The angle between the second and third polarizers is 15 degrees. Applying Malus' law again, we get:

I3 = I2 \* cos^2(15°)

Substituting the value of I2, we get:

I3 = (1/2) \* I0 \* cos^2(40°) \* cos^2(15°)

Now, we need to find the percentage of the original intensity, which is I3/I0. To do this, we can simplify the expression for I3:

I3/I0 = (1/2) \* cos^2(40°) \* cos^2(15°)

Using a calculator to evaluate the trigonometric functions, we get:

I3/I0 ≈ (1/2) \* 0.766 \* 0.933 ≈ 0.358

To find the percentage, we multiply by 100:

(I3/I0) \* 100 ≈ 35.8%

Therefore, the light coming out of the second polarizer has approximately 35.8% of the original intensity.
54.8
DeepSeek-Coder-V2 To solve the problem step by step, we need to apply Malus' law to determine the intensity of the light after passing through each polarizer.

1. **Initial Intensity**:
- The initial intensity of the unpolarized light is \( I_0 \).

2. **First Polarizer**:
- When unpolarized light passes through the first polarizer, it becomes polarized. The intensity of the light after passing through the first polarizer is reduced by a factor of 1/2.
- Therefore, the intensity after the first polarizer is:
\[
I_1 = \frac{I_0}{2}
\]

3. **Second Polarizer**:
- The angle between the first and second polarizers is \( 40^\circ \).
- Using Malus' law, the intensity after the second polarizer is:
\[
I_2 = I_1 \cos^2(40^\circ)
\]
- Substituting \( I_1 \):
\[
I_2 = \frac{I_0}{2} \cos^2(40^\circ)
\]
- Calculating \( \cos^2(40^\circ) \):
\[
\cos(40^\circ) \approx 0.766
\]
\[
\cos^2(40^\circ) \approx (0.766)^2 \approx 0.587
\]
- Therefore:
\[
I_2 = \frac{I_0}{2} \times 0.587 = 0.2935 I_0
\]

4. **Percentage of Original Intensity**:
- The percentage of the original intensity after the second polarizer is:
\[
\text{Percentage} = \left( \frac{I_2}{I_0} \right) \times 100\% = \left( \frac{0.2935 I_0}{I_0} \right) \times 100\% = 29.35\%
\]

Thus, the percentage of the original intensity of the light coming out of the second polarizer is:

\[
\boxed{29.35\%}
\]
54.8
Qwen2-72B-Instruct Let's denote the original intensity of the unpolarized light as $I_0$. When unpolarized light passes through a polarizer, it becomes polarized, and its intensity is halved (since only half of the light is polarized in the direction of the polarizer). Let's call the intensity after the first polarizer $I_1$. According to Malus' law, $I_1 = \frac{1}{2}I_0$.

The light then passes through a second polarizer at an angle of 40 degrees to the first. The intensity of the light after the second polarizer, which we'll call $I_2$, can be found using Malus' law again:

$$I_2 = I_1 \cos^2(40^\circ) = \frac{1}{2}I_0 \cos^2(40^\circ)$$

Finally, the light passes through a third polarizer at an angle of 15 degrees to the second. The intensity of the light after the third polarizer, which we'll call $I_3$, can be found using Malus' law one last time:

$$I_3 = I_2 \cos^2(15^\circ) = \frac{1}{2}I_0 \cos^2(40^\circ) \cos^2(15^\circ)$$

Plugging in the values for $\cos(40^\circ)$ and $\cos(15^\circ)$:

$$I_3 = \frac{1}{2}I_0 (0.7660444431)^2 (0.9659258263)^2 \approx \frac{1}{2}I_0 (0.58657)(0.93301) \approx \frac{1}{2}I_0 (0.54603)$$

$$I_3 \approx 0.273015 I_0$$

Therefore, the percentage of the original intensity that was the light coming out of the second polarizer is approximately 27.30%.
54.8
baichuan4 To solve this problem, we'll use Malus' law twice to find the intensity of the light after passing through each polarizer.

First, let's find the intensity after the light passes through the second polarizer. The angle between the polarized light and the second polarizer is 40 degrees. Using Malus' law:

$$I_1 = I_0 \cdot \cos^2(40^\circ)$$

Next, let's find the intensity after the light passes through the third polarizer. The angle between the polarized light (now coming from the second polarizer) and the third polarizer is 15 degrees. Using Malus' law again:

$$I_2 = I_1 \cdot \cos^2(15^\circ)$$

Substituting $I_1$ from the previous equation:

$$I_2 = I_0 \cdot \cos^2(40^\circ) \cdot \cos^2(15^\circ)$$

Now, we want to find the percentage of the original intensity, which is:

$$\frac{I_2}{I_0} \times 100\% = \cos^2(40^\circ) \cdot \cos^2(15^\circ) \times 100\%$$

Let's calculate the values:

$$\cos(40^\circ) \approx 0.7660$$
$$\cos(15^\circ) \approx 0.9659$$

So,

$$\cos^2(40^\circ) \cdot \cos^2(15^\circ) \approx (0.7660)^2 \cdot (0.9659)^2 \approx 0.5857 \cdot 0.9326 \approx 0.5454$$

Multiplying by 100% gives us the percentage of the original intensity:

$$0.5454 \times 100\% \approx 54.54\%$$

Therefore, the light coming out of the second polarizer was approximately 54.54% of the original intensity.
54.8
doubao For the first polarizer, since the incident light is unpolarized, the intensity after passing through the first polarizer is $I_1 = I_0/2$.

For the second polarizer, the angle between the light and the polarizer is 40 degrees, so the intensity after passing through the second polarizer is $I_2 = I_1 \cos^2(40^\circ) = (I_0/2) \cos^2(40^\circ)$.

For the third polarizer, the angle between the light coming out of the second polarizer and the third polarizer is 15 degrees. So the intensity coming out of the third polarizer is $I_3 = I_2 \cos^2(15^\circ) = (I_0/2) \cos^2(40^\circ) \cos^2(15^\circ)$.

To find the percentage of the original intensity, we divide $I_3$ by $I_0$ and multiply by 100:

$(\frac{I_3}{I_0}) \times 100 = (\frac{(I_0/2) \cos^2(40^\circ) \cos^2(15^\circ)}{I_0}) \times 100 = (\frac{1}{2} \cos^2(40^\circ) \cos^2(15^\circ)) \times 100$.

Evaluating this expression gives the required percentage.
54.8
minimax To solve this problem, we need to apply Malus' law at each polarizer. Let's denote the intensity of the light after each polarizer as I1, I2, and I3 respectively.

1. After the first polarizer, the intensity of the light is given by:
$$ I_1 = I_0 \cos^2(\theta_1) $$
Since the light is initially unpolarized, we can assume that the maximum intensity it can reach after being polarized is I0 (the intensity of polarized light before the polarizer). So, I0 is the intensity after the first polarizer, and we have:
$$ I_1 = I_0 \cos^2(0) = I_0 \cdot 1 = I_0 $$

2. The light then passes through a second polarizer at an angle of 40 degrees to the first. Using Malus' law again:
$$ I_2 = I_1 \cos^2(\theta_2) $$
$$ I_2 = I_0 \cos^2(40^\circ) $$

3. Finally, the light passes through a third polarizer at an angle of 15 degrees to the second. Again, applying Malus' law:
$$ I_3 = I_2 \cos^2(\theta_3) $$
$$ I_3 = I_0 \cos^2(40^\circ) \cos^2(15^\circ) $$

Now we need to calculate the numerical value of $I_3$ as a percentage of $I_0$.

Using a calculator, we find the cosine values:
$$ \cos(40^\circ) \approx 0.766 $$
$$ \cos(15^\circ) \approx 0.966 $$

Now we calculate $I_3$:
$$ I_3 = I_0 \cdot (0.766)^2 \cdot (0.966)^2 $$
$$ I_3 \approx I_0 \cdot 0.586896 \cdot 0.933156 $$
$$ I_3 \approx I_0 \cdot 0.547 $$

To find the percentage of the original intensity, we multiply by 100:
$$ \frac{I_3}{I_0} \times 100\% \approx 54.7\% $$

Therefore, the light coming out of the second polarizer has approximately 54.7% of the original intensity.
54.8
kimi To solve this problem, we need to apply Malus' law at each stage of the light passing through the polarizers.

1. **First Polarizer**: The light starts as unpolarized, so we assume that the average intensity of the light after passing through the first polarizer is half of the original intensity (since unpolarized light has equal amounts of light in all polarization directions, and a polarizer only allows light polarized in one direction to pass through). So, if $I_0$ is the initial intensity, the intensity after the first polarizer, $I_1$, is:

$$ I_1 = I_0 \cdot \frac{1}{2} $$

2. **Second Polarizer**: The light then passes through a second polarizer at an angle of 40 degrees to the first. Using Malus' law, the intensity after the second polarizer, $I_2$, is:

$$ I_2 = I_1 \cdot cos^2(40^\circ) $$

3. **Third Polarizer**: Finally, the light passes through a third polarizer at an angle of 15 degrees to the second polarizer. Again, using Malus' law, the intensity after the third polarizer, $I_3$, is:

$$ I_3 = I_2 \cdot cos^2(15^\circ) $$

Now, let's calculate the final intensity:

1. $I_1 = I_0 \cdot \frac{1}{2}$
2. $I_2 = I_1 \cdot cos^2(40^\circ) = I_0 \cdot \frac{1}{2} \cdot cos^2(40^\circ)$
3. $I_3 = I_2 \cdot cos^2(15^\circ) = I_0 \cdot \frac{1}{2} \cdot cos^2(40^\circ) \cdot cos^2(15^\circ)$

We need to find the cosine values for 40 degrees and 15 degrees:

$$ cos(40^\circ) \approx 0.7660 $$
$$ cos(15^\circ) \approx 0.9659 $$

Now, calculate the squares of these cosine values:

$$ cos^2(40^\circ) \approx 0.7660^2 \approx 0.5868 $$
$$ cos^2(15^\circ) \approx 0.9659^2 \approx 0.9328 $$

Now, calculate the final intensity:

$$ I_3 = I_0 \cdot \frac{1}{2} \cdot 0.5868 \cdot 0.9328 $$
$$ I_3 \approx I_0 \cdot 0.2966 $$

To find the percentage of the original intensity, we multiply by 100:

$$ \text{Percentage of original intensity} = I_3 \cdot \frac{100}{I_0} $$
$$ \text{Percentage of original intensity} \approx 0.2966 \cdot 100 $$
$$ \text{Percentage of original intensity} \approx 29.66\% $$

So, approximately 29.66% of the original intensity of the light was left after passing through the second polarizer.
54.8
wenxinyiyan To solve this problem, we will apply Malus' law to calculate the intensity of light after it passes through each polarizer. Malus' law states that the intensity of polarized light passing through a polarizer is given by $I = I_0 \cos^2(\theta)$, where $I$ is the intensity of the light after passing through the polarizer, $I_0$ is the intensity of the light before passing through the polarizer, and $\theta$ is the angle between the polarization direction of the light and the axis of the polarizer.

1. **First Polarizer**:


* The initial light is unpolarized, so we consider its intensity before the first polarizer to be $I_{initial}$.
* After passing through the first polarizer, the intensity of the light will be reduced to half, as only the component of light along the polarization axis of the polarizer will pass through. Therefore, the intensity after the first polarizer is $I_1 = 0.5 \times I_{initial}$.
2. **Second Polarizer**:


* The light now passes through a second polarizer at an angle of $40^\circ$ to the first.
* Applying Malus' law, the intensity after the second polarizer is $I_2 = I_1 \cos^2(40^\circ)$.
* Substituting $I_1$ from the previous step, we get $I_2 = 0.5 \times I_{initial} \cos^2(40^\circ)$.
3. **Third Polarizer**:


* Finally, the light passes through a third polarizer at an angle of $15^\circ$ to the second polarizer.
* Applying Malus' law again, the intensity after the third polarizer is $I_3 = I_2 \cos^2(15^\circ)$.
* Substituting $I_2$ from the previous step, we get $I_3 = 0.5 \times I_{initial} \cos^2(40^\circ) \cos^2(15^\circ)$.

To find the percentage of the original intensity that is coming out of the second polarizer, we calculate $\frac{I_3}{I_{initial}} \times 100$.

$$\frac{I_3}{I_{initial}} \times 100 = 0.5 \times \cos^2(40^\circ) \times \cos^2(15^\circ) \times 100$$

$$\frac{I_3}{I_{initial}} \times 100 = 0.5 \times (0.7660)^2 \times (0.9659)^2 \times 100$$

$$\frac{I_3}{I_{initial}} \times 100 = 28.29\%$$

Therefore, the percentage of the original intensity of light coming out of the second polarizer is approximately $28.29\%$.
54.8
zhipu To solve this problem, we need to apply Malus' law sequentially to each polarizer. Let's denote the original intensity of the unpolarized light as \( I_{\text{unpol}} \).

1. **First Polarizer:**

When unpolarized light passes through a polarizer, its intensity is reduced by half because the light is now polarized along one axis. Therefore, the intensity after the first polarizer, \( I_1 \), is:
\[
I_1 = \frac{I_{\text{unpol}}}{2}
\]

2. **Second Polarizer:**

The light then passes through a second polarizer at an angle \( \theta = 40^\circ \) to the first polarizer. According to Malus' law, the intensity \( I_2 \) after the second polarizer is:
\[
I_2 = I_1 \cos^2(40^\circ)
\]
Substituting \( I_1 \):
\[
I_2 = \frac{I_{\text{unpol}}}{2} \cos^2(40^\circ)
\]

3. **Third Polarizer:**

The light then passes through a third polarizer at an angle \( \theta = 15^\circ \) to the second polarizer. Again, using Malus' law, the intensity \( I_3 \) after the third polarizer is:
\[
I_3 = I_2 \cos^2(15^\circ)
\]
Substituting \( I_2 \):
\[
I_3 = \left( \frac{I_{\text{unpol}}}{2} \cos^2(40^\circ) \right) \cos^2(15^\circ)
\]
Simplifying, we get:
\[
I_3 = \frac{I_{\text{unpol}}}{2} \cos^2(40^\circ) \cos^2(15^\circ)
\]

To find the percentage of the original intensity that the light coming out of the second polarizer, we need to calculate \( I_2 \) as a percentage of \( I_{\text{unpol}} \):

\[
\text{Percentage} = \left( \frac{I_2}{I_{\text{unpol}}} \right) \times 100
\]

Substituting \( I_2 \):

\[
\text{Percentage} = \left( \frac{\frac{I_{\text{unpol}}}{2} \cos^2(40^\circ)}{I_{\text{unpol}}} \right) \times 100
\]

Simplifying:

\[
\text{Percentage} = \left( \frac{1}{2} \cos^2(40^\circ) \right) \times 100
\]

Now, we need to calculate \( \cos^2(40^\circ) \):

\[
\cos(40^\circ) \approx 0.766
\]

\[
\cos^2(40^\circ) \approx (0.766)^2 \approx 0.586
\]

Substituting this value back into the equation:

\[
\text{Percentage} = \left( \frac{1}{2} \times 0.586 \right) \times 100
\]

\[
\text{Percentage} = \left( 0.293 \right) \times 100
\]

\[
\text{Percentage} \approx 29.3\%
\]

Therefore, the light coming out of the second polarizer is approximately 29.3% of the original intensity.
54.8
gpto1 To solve this problem, we'll use Malus' Law and understand how polarizers affect the intensity of light.

**Step 1: Unpolarized Light Passing Through the First Polarizer**

When unpolarized light passes through a polarizer, the intensity of the transmitted light is reduced by half. This is because the polarizer only allows the component of light polarized along its axis to pass through.

\[
I_1 = \frac{1}{2} I_0
\]

where:
- \( I_0 \) is the original intensity of the unpolarized light.
- \( I_1 \) is the intensity after the first polarizer.

**Step 2: Light Passing Through the Second Polarizer**

The light exiting the first polarizer is now polarized along its axis. When this polarized light passes through a second polarizer at an angle \( \theta_1 = 40^\circ \) relative to the first, Malus' Law applies:

\[
I_2 = I_1 \cos^2 \theta_1
\]

Substituting \( I_1 \):

\[
I_2 = \left( \frac{1}{2} I_0 \right) \cos^2 40^\circ
\]

**Calculating \( \cos^2 40^\circ \):**

\[
\cos 40^\circ \approx 0.7660
\]
\[
\cos^2 40^\circ = (0.7660)^2 \approx 0.5868
\]

**Step 3: Compute the Intensity After the Second Polarizer**

\[
I_2 = \left( \frac{1}{2} I_0 \right) \times 0.5868
\]
\[
I_2 = 0.2934 \, I_0
\]

**Step 4: Calculate the Percentage of the Original Intensity**

\[
\text{Percentage} = \left( \frac{I_2}{I_0} \right) \times 100\%
\]
\[
\text{Percentage} = (0.2934) \times 100\% \approx 29.34\%
\]

**Answer:**

Approximately 29% of the original intensity comes out of the second polarizer.
54.8
deepseekv3 To solve this problem, we'll apply **Malus' law** step by step as the unpolarized light passes through each polarizer.

---

### Step 1: Unpolarized light passes through the first polarizer
Unpolarized light has equal intensity in all directions. When it passes through the first polarizer, only the component of light aligned with the polarizer's axis is transmitted. The intensity after the first polarizer is:

\[
I_1 = \frac{I_0}{2}
\]

where \(I_0\) is the original intensity of the unpolarized light.

---

### Step 2: Light passes through the second polarizer (angle = 40°)
The light exiting the first polarizer is now polarized. It passes through the second polarizer, which is at an angle of \(40°\) relative to the first polarizer. Using Malus' law:

\[
I_2 = I_1 \cos^2(40°)
\]

Substitute \(I_1 = \frac{I_0}{2}\):

\[
I_2 = \frac{I_0}{2} \cos^2(40°)
\]

---

### Step 3: Light passes through the third polarizer (angle = 15°)
The light exiting the second polarizer is now polarized at \(40°\) relative to the first polarizer. It passes through the third polarizer, which is at an angle of \(15°\) relative to the second polarizer. The total angle between the first and third polarizers is \(40° + 15° = 55°\). Using Malus' law:

\[
I_3 = I_2 \cos^2(15°)
\]

Substitute \(I_2 = \frac{I_0}{2} \cos^2(40°)\):

\[
I_3 = \frac{I_0}{2} \cos^2(40°) \cos^2(15°)
\]

---

### Step 4: Calculate the percentage of the original intensity
The intensity of the light exiting the third polarizer as a percentage of the original intensity \(I_0\) is:

\[
\text{Percentage} = \frac{I_3}{I_0} \times 100 = \frac{\frac{I_0}{2} \cos^2(40°) \cos^2(15°)}{I_0} \times 100
\]

Simplify:

\[
\text{Percentage} = \frac{1}{2} \cos^2(40°) \cos^2(15°) \times 100
\]

Now, calculate the numerical values:

1. \(\cos(40°) \approx 0.766\)
2. \(\cos(15°) \approx 0.966\)

Substitute these values:

\[
\text{Percentage} = \frac{1}{2} (0.766)^2 (0.966)^2 \times 100
\]

\[
\text{Percentage} = \frac{1}{2} (0.586) (0.933) \times 100
\]

\[
\text{Percentage} = \frac{1}{2} (0.547) \times 100
\]

\[
\text{Percentage} = 0.2735 \times 100
\]

\[
\text{Percentage} = 27.35\%
\]

---

### Final Answer:
The light exiting the second polarizer has **27.35%** of the original intensity.
54.8