Refractive Index of a Liquid and Temperature

Contents

Introduction

Research Question

Research Hypothesis

Methodology

Materials

Procedure

Safety Precautions

Results

Graphs

Data Analysis

Discussion and Conclusion

References

Introduction

After learning the refractive index concept in class, I started wondering what will be the effect of changing temperature on the refractive index. Being a fan of swimming, concepts of apparent and real depth have always been fascinating to me. In this IA, I wanted to explore how the apparent and real depth of a liquid would change with an increase in temperature at different times of the day. The speed of light keeps changing as light moves from one medium to another of different optical densities. For instance, the speed of a ray of light moving from a denser medium to a rarer medium will decrease (Bhattacharjee, 2018). If the ray reverse in the same direction, this time moving from a rarer medium to a denser medium, its speed will increase.

Ideally, when the ray moves from a denser medium to a rarer medium, its particles collect together, hence reducing speed. On the other hand, when the ray is moving from the rarer medium to a denser medium, its particles spread out, and speed increases.

Light is a form of transverse wave (Dahan et al., 2020). A transverse wave is produced when particles of the medium vibrate perpendicularly or right angles (Karami et al., 2019). The velocity of that medium is a product of wavelength and frequency. However, a shaft in transverse wave causes bending of the incident ray as it passes from one medium to another, and incidentally, a change in refracted ray. The ratio of real depth to apparent depth, the sin of the angle of incidence to sin of the angle refraction of actual speed in a medium to light of light constitutes the refractive index, n (Bhattacharjee, 2018). Therefore;

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The terms i and r refer to the angle of incidence and the refraction angle, respectively, as shown in figure 1 below.

Editorial Note: Figute 1 was removed due to copyright issues

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Figure 1: Angle of incidence and angle of refraction at point of incidence

Refraction is guided by Snell's law, which states that "the ratio of the sine of the angles of incidence and transmission is equal to the ratio of the refractive index of the materials at the interface." (Karami et al., 2019). Supposing a ray of light moving from a rarer medium (air) and moving towards a denser medium, in this case into a liquid, the angle of incidence will as it moves towards the normal at point of incidence. The angle of refraction will increase, increasing the refractive index. Incidentally, the refractive index will be more than one. This study will evaluate how the refractive index will be affected by the change in temperature.

Research Question

Does the refractive index of a liquid vary with temperature?

Research Hypothesis

An increase in temperature will increase the liquid's refractive index when temperature of a liquid leads to a reduction of its density, which raises the refractive index.

Methodology

Variables

There are several variables to be controlled in this experiment.

- Independent Variables. The main independent variable in this experiment is temperature of water liquid and angle to hold the laser.
- Dependent Variables. The main dependent variable in this investigation is the refractive index. The Refractive index will be changing with a variation of temperature.
- Control Variables. The main control variables are the amount of liquid water and the size of the container holding the liquid.

Table 1: Dependent and Independent Variables

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Table 2: Control Variables

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Materials

Table 3: Material, Quantity and Specifics

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Procedure

1. Create the set-up. Cut and size the cardboard in such a way that it stand in a right angle (perpendicular) to the ground.
2. Tape the meter ruler and fix it to the cardboard ensuring that it is suspended accordingly, to laser's height.
3. Place the quadrilateral tank in such a way that it stands in front of the cardboard. Thereafter, attach one of the protractors with its two sides, ensuring that its center aligns with the center of quadrilateral tank.
4. Fix the laser system onto the stand, shining via the center of quadrilateral tank and parallel to the ground level at 200.
5. Measure 500ml of water using the graduated measuring cylinder into the refrigerator. Then measure and heat another 500ml of water into a beaker and heat on a Bunsen burner.
6. Place the heated 500ml of water into the quadrilateral tank and insert the thermometer to take readings of temperature.
7. Identify a point where laser lands, stretch a line and connect the protractor to record angle of refraction
8. Repeat steps 1 to 7 for four more trials.
9. Repeat steps 1 to 8, placing water at 500C, 400C 300C and 100C.

Editorial Note: Figute 2 was removed due to copyright issues

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Figure 2: Set-up of the experiment

Safety Precautions

1. An appropriate distance was ensured from the hot water and Bunsen burner. PVC gloves were worn when handling the hot beaker.
2. Same level was ensured between the laser and quadrilateral tank that was holding water.

Results

Raw Data

Table 4: Angle of incidence and angle of refraction of, water at 500C

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