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# Determining the Type of Particle in an Air Sample by Using Laser Light Scattering

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Contents

## Introduction

In this experiment(Determining the Type of Particle in an Air Sample by Using Laser Light Scattering), we will be correlating different types of particles by observing their scattering properties of laser light.

We hypothesised that the type of particle could correlate by analysing their laser light scattering property.

## Aim

To correlate the different types of particles based on their property of laser light scattering.

## Theory

1. Scattering of light in a medium is performed by the particles in that medium.

2. Greater the number of particles, the more scattering of light will be.

## Requirements

1. Circular tube,

2. A laser,

3. A digital camera,

4. A filter paper,

5. A fan,

6. A computer,

7. A notebook,

8. Flour,

9. Sawdust.

## Procedure

Step 1: Set up a circular tube so that air circulates through it.

Step 2: Point a laser through the opening of the tube.

Step 3: Set up a digital camera at an angle to the laser beam.

Step 4: Clean the air by placing the filter on the in-valve.

Step 5: Take three pictures of clean air as a control.

Step 6: Place the sample inside the in-valve.

Step 7: Turn on the fan.

Step 8: Take four pictures of the air with samples in it.

Step 10: Using a program, find out the brightness of the beam for each of the angel numbers.

Step 11: Now, graph the valve.

## Observation

1. Our hypothesis was partly correct.

2. Performing this experiment with the given tools was a difficult task.

3. We saw a difference in the graph obtained. The smoother graph was of uniform composition, and the composition, which had a mixture of small particles and large particles, had a greater difference between lows and highs.

4. Once we obtained the graph of a certain particle, we compared the result with the graph of an unknown substance. And in this way, we determined the type of unknown substance. Therefore, we can determine the type of particle just by its laser light scattering property.

## Result

1. The graph of the angle number Vs brightness for all the four samples were different from each other.

2. There was no brightness when we cleaned the air.

3. Flour and sawdust produced the most brightness. Their brightness level was 255, which was also the limit of cameras. Therefore the graph of sawdust and flour peaked.

## Precautions

1. Clean the air inside the in valve thoroughly.

## Conclusion

In this experiment, we determined whether the scattering of laser light finds out the relative size of particles. And we also correlated the type of particles with their angle Vs intensity graph.

Q.1 What was the aim of your experiment?

ANS. We aimed to correlate the different types of particles based on their property of laser light scattering.

Q.2 Why it was difficult to perform this experiment with the given materials?

ANS. Performing this experiment with the given materials was difficult because of the small size of the particles.

Q.3 Which one had the smoother graph?

ANS. The smoother graph was of uniform composition (all the particles had the same size).

Q.4 Which composition had the non-smoother graph?

ANS. The composition, which had a mixture of small particles and large particles, had a greater difference between lows and highs in the graph.

Q.5 Why was there no brightness when you cleaned the air inside the valve?

ANS. As there were no particles that might perform the scattering of light. As a result, there was no brightness.

Q.6 What kind of particles produced most of the brightness?

ANS. The particles of flour and sawdust produced most of the brightness.

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