the relationship between the salinity of water and the refractive index of water

In this experiment, there are some values that cannot be reached by using specific instruments. So some calculations must be done to determine the indices of saline water at different salinity rates. So Snell’s law must be used. Because I assume I prepared the experiment in the ideal air, I will assume its refractive index is 1.

 

\(n1\ \times\ sin\alpha=n2\ \times\ sin\beta\)

 

We will assume that n1 is equal to 1 because of air.

 

For the 5 grams of salt

 

\(\alpha\ = 42º,\ _{n_1}=1\ ........\ \beta=33.5º,\ n_2=\ ?\)

 

\(sin\alpha=sin42.0º=0.6691\)

 

  Error = (sin 43 - sin 41 ) \ 2 = 0.0129

 

\(Sin\alpha=0.6691\ \pm0.0129=0.6691\ \pm1.92\%\)

 

\(sin\beta=sin33.5º=0.5519\)

 

  Error = (sin 34.5 - sin 32.5)\ 2 = 0.0145

 

\(Sin\beta=0.5519\ \pm0.0145\ =0.5519\ \pm\ 2.62\%\)

 

 

\(n_1\ \times\ sin\alpha=n_2\ \times\ sin\beta\)

 

\(1\ \times\ sin42=n\ \times\ sin33.5\)

 

\((1\ \times\ sin42)\ / \ sin(33.5)\ = 1.2123\)

 

Error = 1.92 + 2.62 = 4.45%

 

\(1.2123\ \pm\ 4.54\%\)

 

 

For the 10 grams of salt

 

\(\alpha=42°,\ n_1=\ 1\ ........\ \beta=33.0°,n_2=\ ?\)

 

\(sin\alpha=sin42.0°=0.6691\)

 

Error = (sin 43  - sin 41) \ 2 = 0.0129

 

\(sin\alpha=0.6691\ \pm\ 0.0129=0.6691\ \pm\ 1.92\%\)

 

\(sin\beta=sin33.0°=0.5446\)

 

Error = (sin34.0 - sin32.0) \ 2 = 0.0146

 

\(Sin\beta=0.5446\ \pm\ 0.0146\ = 0.5446\ \pm\ 2.68\%\)

 

\(n_1\ \times\ sin\alpha\ = n_2\ \times\ sin\beta\)

 

\(1\ \times\ sin42\ = n\ \times\ sin33\)

 

\((1\ \times\ sin42)\ / \ sin(33)\ = 1.2286\)

 

 

\(1.2286\ \pm\ 4.60\%\)

 

 

For the 15 grams of salt

 

\(\alpha=42°,\ n_1=\ 1\ ........\ \beta=32.0°,n_2=\ ?\)

 

\(sin\alpha\ = sin42.0°\ = \ 0.6691\)

 

 

\(Sin\alpha\ = 0.6691\ \pm\ 0.0129=0.6691\ \pm\ 1.92\%\)

 

\(sin\beta\ =sin32.0°=0.5299\)

 

 

\(Sin\beta=05299\ \pm\ 0.0148=0.5299\ \pm2.79\%\)

 

\(n_1\ \times\ sin\alpha=n_2\ \times\ sin\beta\)

 

\(1\ \times\ sin42\ = n\ \times\ sin32\)

 

\((1 \times\ sin42)\ / \ sin(32)=1.2626\)

 

 

\(1.2626\ \pm\ 4.71\%\)

 

 

For the 20 grams of salt

 

\(\alpha\ = 42°,\ n_1\ = 1\ ........\ \beta=31.5°,\ n_2\ =\ ?\)

 

\(sin\alpha=sin42.0°=0.6691\)

 

 

\(Sin\alpha=0.6691\ \pm0.0129\ = 0.6691\ \pm\ 1.92\%\)

 

\(sin\beta=sin31.5°=0.5224\)

 

 

\(Sin\beta= 0.5224\ \pm\ 0.0148\ =0.5224\ \pm\ 2.83\%\)

 

\(n_1\ \times\ sin\alpha=n_2\ \times\ sin\beta\)

 

\(1\ \times\ sin42\ = n\ \times\ sin31.5\)

 

\((1\ \times\ sin42)\ / \ sin(31.5)=1.2808\)

 

 

\(1.2808\ \pm\ 4.75\%\)

 

 

For the 25 grams of salt

 

\(\alpha\ 42°,\ n_1=1\ ........\ \beta=30.5°, n_2=\ ?\)

 

\(sin\alpha=sin42.0°=0.6691\)

 

 

\(Sin\alpha=0.6691\ \pm\ 0.0129=0.6691\ \pm\ 1.92\%\)

 

\(sin\beta\ =sin30.5°\ =\ 0.5075\)

 

 

\(Sin\beta=0.5075\ \pm\ 0.0150=0.5075\ \pm2.95\%\)

 

\(n_1\ \times\ sin\alpha=n_2\ \times\ sin\beta\)

 

\(1\ \times\ sin42=n\ \times\ sin30.5\)

 

\((1\ \times\ sin42)\ / \ sin(30.5)\ =\ 1.3184\)

 

 

\(1.3184\ \pm\ 4.87\%\)

 

 

For the 0 grams of salt

 

\(\alpha=42°, n_1=1\ ........\ \beta=34.0°, n_2=\ ?\)

 

\(sin\alpha=sin42.0°=0.6691\)

 

 

\(Sin\alpha=0.6691\ \pm\ 0.0129=0.6691\ \pm\ 1.92\%\)

 

\(sin\beta =sin34°=\ 0.5591\)

 

 

\(Sin\beta\ = 0.5591\ \pm\ 0.0144\ =0.5591\ \pm\ 2.57\%\)

 

\(n_1\ \times\ sin\alpha\ =n_2\ \times\sin\beta\)

 

\(1\ \times\ sin42\ =n\ \times\ sin34\)

 

\((1\ \times\ sin42)\ / \ sin(34)\ =\ 1.1967\)

 

 

\(1.1967\ \pm\ 4.49\%\)

 

Average Error of Refractive Index.

 

 

\((4.49\ +\ 4.54\ +\ 4.60\ +\ 4.71\ + \ 4.75\ +4.87)\ /\ 6=4.66\%\)

Figure 1 shows a diagram of light traveling through a different medium and refracting in that medium. The refractive indices of the two media are indicated by n₁ and n₂, and the angles between the light beam and the line perpendicular to the medium and  \(\theta_1\), \(\theta_2\)  separation line are indicated by.

 

The equation's discovery can be traced back to ancient Egypt. However, Thomas Harriot is credited with being the first physicist to find this equation. He worked on this equation for a while, but he passed away before he could publish it. Then, Willebrord Snellius, the person I previously mentioned, conducted some experiments and discovered this equation, but, like Harriot, he chose not to publish it.

 

Then, in his renowned work "Discourse on Method," the well-known philosopher Descartes published this equation. This equation has several names in various nations due to the fact that numerous scientists have worked on it and produced the same result.

 

The wave phenomenon of light explains this behavior of light. Every location where light can travel has an index that governs how light behaves in that medium. Following the assumption that the vacuums index is 1, these medium indices are generated The smallest index that a medium can have is 1, and all other media are supposed to have greater indices than 1 to apply Snell's law

 

The definition of this behavior of light in terms of physics is "The phenomenon known as refraction is caused by the difference in the speed of propagation of light in different mediums."

 

Additionally, external factors like alterations in pressure, temperature, salinity, etc. can alter the refractive indices of the media. By simply observing a fish in a river and another fish in the sea that is both keeping at the same depth from the surface of the water, we may notice this change in nature. The fish can be seen closer to the surface in the sea than in rivers because the sea has a higher salinity than rivers.

 

This experiment will look into the connection between changes in refractive index and salinity of pure water. The main goal is to observe light refraction in clear water at various salinity levels.

 

By examining the angles between the light beams and the normal line, which is perpendicular to the line separating the mediums, Snell's law can be utilised to assess the impact of salinity. The medium's index can then be established.

The impact of salinity on water's refractive index is covered in this thesis. The association between saline concentration of water and the refractive index of water is studied in numerous experiments and measurements to demonstrate this effect.

 

The link is determined that when water salinity rises, the refractive index also rises. Graph 1.1 provides evidence for this. We can see that this is a linear line because the graph's equation is similar to y = mx + n. The graphic and x-axis make an acute angle with a positive slope and m value. These indicate a positive, linear, increasing equation in the equation and graph. Consequently, the refractive index rises as the amount of salt in the water do.

 

The seas and oceans are where we may see this effect the most. Seas and oceans differ in salinity from one another. This impacts the light refracted from the ocean's or sea's surface. The amount of light that penetrates the ocean's surface has an impact on living organisms. There are three main sea zones, each with a varied degree of light reach and a range of animal and plant life. The three marine regions in question are the daylight zone, the twilight zone, and the midnight zone. The three primary zones are completely diverse aquatic worlds with unique qualities. In addition to these zones, the coastline is frequently considered a separate sea region because it can also indicate a particular marine activity. Since the sunlight zone is closer to the surface of the water, it also receives the most light. More than 90% of marine species can exist in this area thanks to the water and light balance. In addition, because of how much light plants get in the sunlight zone, it is the only one where they can survive. The twilight zone is the second sea region. Sealife like shrimp and squid can be found in this area. The third sea region, often known as the midnight zone, is a deep, black section of the ocean where light cannot penetrate. Only 1% of sea species are found in this region, where sharks and other animals have habitats. Near-freezing temperatures and high water pressure are both present in the midnight zone. This remark demonstrates how the zones are directly impacted by salinity since the intensity of the sunlight produces them.

 

I proposed a direct association between salt concentration and refractive in my theory. My hypothesis is true, and there is a direct correlation between them, according to the experiment I conducted and the measurement I did. The experiment's goals are thus met, and the correlation is computed.

 

There are several errors in the experiment that has affected the result,

 

• The temperature change has a direct impact on the refractive index. According to legend, the refractive index rises as the temperature rises. In my experiment, I measured the temperature of the saline water before adding it to the semi-circular beaker so that the water's temperature could be adjusted afterwards. Therefore, this might have an impact on what I found.

 

• The water in the semi-circular beaker needs to be steady to be able to see the refraction. If not, it's possible that there will be a variety of refractions, making it impossible to spot steady, consistent refraction. Because of the parameters in my experiment, the table I used for the experiment is essentially stable. If you touch it, it still trembles. I made an effort to prevent this and gave the water some time to stabilize, but the findings of my experiment may still be affected.

 

• A needle is positioned in the laser light's direction following refraction, as I indicated in my method. However, because of the large radius of the laser light, it was difficult for me to take precise measurements. Depending on the direction of the laser light, the needle I place there may move. The measured angles may change as a result.

 

• Since I studied the relationship between salinity and refractive index in my experiment, the salts I add to the water must be thoroughly blended. To accomplish this, I heated a special mixer to blend the ingredients more effectively. But as it cooled, I noticed that some salt crystals had formed. As a result, my experiment suffers, and my concentration is altered.

 

Systematic mistakes were made in this experiment as a result of temperature variations and salt precipitation. The refractive index is significantly influenced by temperature. Taking this into account, I attempted to experiment at a constant 27 °C, however, because the room's temperature is unstable, the water used for the experiment experienced a shift in temperature. The key independent variable I used in this experiment was salt concentration. I attempted to make concentrated saline water with 5%, 10%, 15%, 20%, and 25% salt. But these salts in the water are exceedingly difficult to dissolve. I finally finished blending most of the salt. But after some time, I noticed little salt particles, indicating that they had precipitated. These issues, including temperature and salt precipitation, affect the data. They so committed a deliberate error.

 

My other faults, such as stabilizing the table I used and the laser light's radius, are supposedly random errors. I kept the table stationery in most of my experiments and obtained precise results. Still, in a few experiments where I tried to open the laser, the table's stability was compromised, and those experiments encountered this inaccuracy. In all my testing, the laser light's radius has not presented a challenge. I placed the needle at the side of the laser light, but in some trials, it was difficult to tell which side the light was coming from, thus, my needle somewhat slipped. Because I used those needles to measure the angle in my experiment, this directly impacted it.

 

My experiment can be modified to produce better results. To improve it, there are some suggestions and ideas. To start, a stable experiment area can be made, which will stop the water level from moving. To increase measuring accuracy, a better laser with a smaller radius might be employed. It can be blended several times to help the full salt dissolve in the water. This will stop the precipitation and produce a concentration that is more precise. The experiment can be carried out in a closed system whose temperature can be managed in order to regulate the temperature change. Thus, this will result in less heat transmission and, as a result, less temperature change. The refractive index can then be determined devoid of the influence of temperature.

Research Question: How does the amount of salt in water affect the refractive index of the water?

 

Purpose. Observe and quantify the link between pure water's salinity and its refractive index at various salinity levels.

 

Hypothesis. The refractive index of water will rise as the saline percentage of the water rises, according to the hypothesis

 

Independent variable: the weight in grams of salt added to the water.

 

Water's refractive index serves as a dependent variable.

 

Constant Variables.

 

• The temperature was measured using a thermometer right before data collection in the same room, treated as if it were an isolated system, with the doors and windows closed.

 

• Using the same space, it is presumed that the pressure will remain constant over a brief period.

 

• Water volume can be determined by using a graduated cylinder to gauge the amount of water before adding salt to it.

The data that was collected from the 6 experiments are above given. Then I wrote an average of each experiment in table 2.1. I used the formula.

 

\(R=Refraction\ Angel\)

 

\((R_1\ + \ R_2\ + \ R_3\ +\ R_4 \ +R_5)\ /\ 5=Range\)

A method was built to observe the refractive index of water at various salt concentrations.

 

Stabilized on a table is cardboard. To calculate the angles, an A4 piece of paper has adhered to it. The semi-circular beaker is then taped to the paper with its side drawn on it and its semi-circular line parallel to the side of the A4 paper. On the paper, the circle's center has been marked. Is drawn a line that goes through that location and is parallel to the side of the. This will serve as the reference line and make it easier to calculate the angle. The semi-circular beaker's center is the target of a laser that has been stabilized close by. To figure out the incident angle, a line that the laser crosses is drawn. The table holding the equipment is moved to a darker area so that it is easier to see the laser light properly.

 

With the aid of a graduated cylinder, 100ml of pure water is obtained after this system has been built. The beaker is then filled with this water. There are 30 repetitions of this method. So each beaker now contains 100ml of water. To ensure that we don't forget which beaker contains how many grams of salt, we've divided the beakers into six groups. The weigher is then utilized for salts after this separation. The first beaker is filled with five grams of salt. After that, 5 grams of salt are added to the remaining 4 beakers in that group. For the following group, 10 grams of salt are added to each beaker.

 

This procedure is carried out for the other 3 groups, which will each contain 15, 20, and 25 grams of salt. The final group serves as the experiment's control group because it contains no salt.

 

With the aid of electromagnetic forces, the mixer that will be utilized in the experiment has the capacity to heat while mixing the water. The beaker is filled with a magnetic fish, and it soon begins to stir. Additionally, the heater, which is positioned beneath the beaker, heats the vessel.

 

The experiment for the first control group will be carried out while the heater on the mixer is opened. To heat the beaker to 30°C, it is placed on the mixer. When the thermometer reads 30°C, water is poured into the semi-circular beaker, which has been punctured with a thermometer. The laser is then opened when the lights go out. A hole in the paper is created when the needle is poked in the direction of the light. After the marking procedure, a straw is used to remove the water from the beaker. The straw aids in sucking up the water, which is then spitting into the sink. This procedure is repeated for the other 4 beakers, which contain no salt, once all the water has been removed.

 

The second group has 5 grams of salt in it. The mixer is turned on to agitate while heating after the magnetic fish has been added to the beaker. When the thermometer reads 30°C, the heating is turned off. The beaker is poured into a semi-circular beaker once the whole salt has been blended. The lights are then turned off, and the laser is activated. The light ray's path is marked by the needle. The water is then drawn out using a straw, leaving the semi-circular beaker empty. For the other beakers, which contain 5 grams of salt, this procedure is repeated four times.

 

The procedure used for group 2 is then repeated for groups 3, 4, and 5, and 6, accordingly. Each beaker is combined, brought to a temperature of 30 °C, poured, and the refraction is gauged. Constant pressure conditions are produced by conducting the experiment in the same space.

 

After the experiment the A4 paper is taken from the system and the beaker is taken from the top of the paper. With the help of a ruler, the hole that the needle created is connected to the intersection of normal line and side line of the beaker. By using the angle meter the diffraction angles are measured 

A graduated cylinder is used to measure the amount of water. I submerge an analogue thermometer in the water to gauge the temperature. These data were used by me to confirm that the experiment's conditions were constant (control the controlled variables and make sure they are constant).

 

Second, I used a weigher to calculate the weight of the salt. I measured the influence of salt weight on the refraction indices of water.

 

An angle metre is used to measure the incidence and refraction angles. I measured these by making lines on the sides of the semi-circular beaker and the directions the laser ray took. I will use these angles to calculate the salinity indices of the water. For this, I'll apply Snell's law.

 

Since the experiment is conducted in the same room for a brief period, it is also claimed that the pressure there remains constant.

The purpose of this lengthy essay is to investigate how changes in the salt content of water affect the refractive index of water. An experiment was conducted to determine the impact of water salinity on its refractive index.

 

The semi-circular beaker's centre is illuminated by a laser beam, and it contains water with various salt concentrations, including 5%, 10%, 15%, 20%, and 25%. The Snell Law is used to calculate the refractive indices of each concentration by measuring the angles from which the laser light entered the beaker and from which it emerged. The graph of salt content vs refractive index was also created using a computer application (Logger Pro 3.8). The link between salt concentration and refractive index was established with the aid of this graph.

 

The experiment's findings show that the salt concentration and refractive index directly correlate with one another. This is demonstrated by the graph, which demonstrates that it is a linear, growing graph, using the equation. The origins of errors are then assessed, and it is established which errors are random and systematic. It is made to connect the experiment's findings to the natural world, and the impact of salinity on the environment is examined. To improve the experiment, several suggestions and tips are offered.

As seen by scientists, light travels at a constant speed in a vacuum, which is estimated to be 3 x 10⁸ m s^-1. It is incredibly challenging to conduct experiments with light at this speed because we humans cannot achieve it. However, we can see in nature various characteristics of light. Someone imprisoned in there for a long time can experience mirages, just like in deserts. These are what are known as mirages, or optical illusions. But it has a straightforward explanation in physics, which was first discovered by Willebrord Snellius (Snell), who provided an equation for this characteristic of light. 

Pure water (3L)

 

Graduated Cylinder (±0.5 ml)

 

Beaker (x30)

 

Semi-circular beaker

 

Laser (Green Laser, 100mW power,)

 

Heating Mixer

 

Salt (300gr)

 

Thermometer (analog, ±0.5ºC)

 

A4 Paper

 

Needle

 

Tape

 

Weigher (digital, ±0.5gr)

 

Straw

 

Ruler (±0.5mm)

 

Angle Meter (±0.1º)