• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Refractrometry. Aim: Using a model Pulfrich refractometer determine the refractive index of a range of sugar solutions and hence determine the refractive index of some sugar solutions with an unknown concentration.

Extracts from this document...

Introduction

Physics Coursework: Refractometry

Introduction

When light crosses the boundary between two materials, it changes its speed and normally its direction, this is refraction. The refractive index (  ) for a pair of materials is a ratio of the wave velocities.

image00.jpg

The incident and refractive angles are measured from the normal (perpendicular to the object).

Aim: Using a model Pulfrich refractometer determine the refractive index of a range of sugar solutions and hence determine the refractive index of some sugar solutions with an unknown concentration.

The following equations show how we can combine different equations for refractive index to come up with one that is useful for  my experiment

The refraction from liquid to glass:

The refraction index from air to glass:

And if:

Then:

And if:

Then:

Using these we can calculate the refractive index from air to liquid is:

We also know that C = 90° - r (because we will use a right-angled block) so sin C = cos r

In conclusion we can come up with a final equation for the refractive index for air to liquid is:

I will then plot the refractive index against the concentration of the sugar solution and draw a line of best fit. From the line of best fit and the refractive index of my unknown concentrations I should then be able to draw a line down from the line to determine the concentration.

...read more.

Middle

Whenever using glass wear care should be taken to minimise the chance of breakage, e.g. keep it well on the bench.

Variables:

My input variable will be the concentration of the sugar solution. I will use a fairly broad and evenly spaced range of concentrations to ensure my graph is accurately drawn and leaves little space to miss important changes in correlation.

This should give me an output variable of refractive index which I will calculate using the equation I have stated previously.

There will be a few control variables that I will have to ensure are kept constant to maintain the credibility of my experiment:

  • The same Perspex block should be used so that the refractive index that I am measuring is the same throughout the experiment.
  • I will use the same equipment for the whole experiment to reduce variation in accuracy and sensitivity, for example different types of black paper may alter the accuracy of my experiment.
  • An especially important part of apparatus to keep constant is the measuring equipment (ruler and protractor), as they may have variations in the accuracy of their scale. The scale at which I am able to read the protractor will affect the sensitivity of my investigation.
...read more.

Conclusion

Concentration of A ~ 11.0%

Concentration of B ~ 26.5%

 Looking at my graph I could say that there were no anomalies in this set of results as I have decided to use the first and last concentration in my line of best fit, however they could be excluded as they are not quite as in line with the others.

As I could not use my results because of their inaccuracy, there must have been considerable accuracy/sensitivity problems in my experiment. I think that probably the most considerable error was human error in distinguishing with our eyes the disappearance of the black paper. If I did this experiment again I would take a range of readings with the pins; one when the black paper first starts to disappear and one when the paper has completely disappeared. I would then take a mid-point of this range as my value.

I also think that the sensitivity in my protractor was limited as I could only read it accurately to ±0.5º, and as the angles were so close it would have been better to have used a more accurate measuring tool.

In conclusion, I am disappointed that my results did not work as I controlled all independent variables etc to ensure the reliability of the experiment. This shows that the sensitivity and accuracy of this experiment is poor, however with a good set of results I feel I came to a good conclusion of concentrations

Annie Rankin        Physics Coursework        May 2006

...read more.

This student written piece of work is one of many that can be found in our GCSE Waves section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Waves essays

  1. Marked by a teacher

    Investigation:To find the refractive index of cooking oil.

    4 star(s)

    ensure that the correct method is being used to test the substance ethanol and water. Six angles of refraction will be found. During the final experiment, this will not be changed. Instead of this, repeats will be performed for the same substance, which is cooking oil.

  2. Marked by a teacher

    Find the critical angle and refractive index for plastic using a graphical treatment for ...

    4 star(s)

    I will do this so the points become positively correlated and can have a line of best fit placed through them. I will use the line of best fit to check any anomalies and find the Sine R value of 1 (900).

  1. Marked by a teacher

    Is Sunbathing Good?

    4 star(s)

    Pg3 UV and your health... Using sun beds can be safe if you follow certain rules that are given with the machine. One example of this is a Instruction book that comes with a Phillip sun bed. UV sessions: You may have one UV session per day, over a period of five to ten days.

  2. Deviation of Light by a Prism.

    of light down the line of incidence that has already been drawn. Moving the prism as close as possible ensures that the beam is small and accurate, and that not much dispersion (the spreading out of a light ray as it enters takes place, because even though the size of

  1. Light is so common that we often take it for granted.

    This idea of light as a wave was popular because it explained experiments in which light created a series of bright and dark lines called an interference pattern. Scientists could explain such interference patterns only by describing light as a wave.

  2. Investigating the factors which affect the sideways displacement of a light ray through a ...

    Underneath is the table of results and graph from my preliminary experiment of i-r. angle of incidence angle of refraction I-r 0 0 0 10 6.5 3.5 20 13 7 30 19 11 40 25 15 50 30 20 60 34 26 70 38 32 80 41 39 * Scientific

  1. Compare the measured refractive index of three liquids against the unknown values and to ...

    The angles I will be using to measure the Refractive Index will be 10o, 20o, 300, 40o, 50o and 60o. I have decided to use these angles because they are at regular intervals and they are easier to work out.

  2. The aim of my experiment is to see what factors affect electromagnetism the most ...

    final results afterwards to see which is the most efficient factor to make the electromagnet stronger. To get the results of these two factors I will have to vary them within separate tests. To increase the accuracy of my results I will also repeat these tests.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work