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

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

Extracts from this document...


Gurveer Saggu

Investigating Refraction

Aim: Find the critical angle and refractive index for plastic using a graphical treatment for my results.

Introduction: The Refractive Index is how the much a material bends the light. In this experiment I will be looking at the how much the angle of incidence gets refracted and I will multiply my results by sine. I will plot a graph from my results and, using a line of best fit, I will calculate the size of the angle of incidence in order for the refracted angle to be equal to 900 (critical angle). I will then calculate the refractive index by using Sine I and Sine R. I will be looking at light going from glass to air (from a dense medium to a lighter one).

Theory: Incident ray: Ray of light before refraction. Angle of refraction (R): Angle between refracted ray and normal at point of incidence. Angle of incidence (I): Angle between incidence ray and normal at point of incidence. Point of incidence: Point at which incident ray meets boundary and becomes refracted ray. Critical angle

...read more.




  1. Arrange the equipment as shown.
  2. Then in the middle of the paper, draw around the block of plastic and keep it placed there.
  3. Then around the curved part of the diagram mark out the normal line, then mark out the angles in 50 intervals.
  4. Connect the PSU to the mains socket and then the ray box to the PSU.
  5. Fit the slit on the ray box allowing only a small ray of light through.
  6. Then turn on the PSU.
  7. Then shine the light on the interval and make sure it comes out of the centre of the straight side.
...read more.


0, then the answer would be 20% incorrect. By showing that the critical angle is slightly out by a degree either side shows that these marginal errors have been taken into account.

Evaluation: My method of carrying out the experiment was good and very simple to follow. Before this version of the experiment, I performed a trial and error attempt of the experiment to get an approximate idea of what the angle would be. Some errors were caused by simple things like rounding an angle to certain decimal places and misjudging an angle. If I were to redo the experiment again then I would take these factors into account and make sure that they would not have a significant effect on the final results. These improvements would make my results more accurate.

My results were valid as they allowed me to get an accurate line of best fit which was important in calculating the critical angle. The results were all along the line of best fit, which was as I had predicted. My results did not have any anomalies which did not affect my results. This conclusion led me to a final conclusion of the critical angle was 430 and the refractive index of the critical angle was approximately 1.28.

...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

Here's what a teacher thought of this essay

4 star(s)

This is a well structured and well written report.
1. The sources of information need to be referenced.
2. The conclusion needs to quote data from the investigation to back up the patterns.
3. The evaluation should suggest further research opportunities.

Marked by teacher Luke Smithen 13/08/2013

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

    refraction experiment

    4 star(s)

    * Make sure that angle of incidence is measured rightly and that the incident ray is drawn in the right manner. * Make sure that the laser shone correctly over the line drawn for the incident ray, so that you get an accurate refracted ray.

  2. Marked by a teacher

    An investigation into the factors affecting the frequency of a standing wave

    4 star(s)

    One way of checking this was to plot the wavelength against the reciprocal of the frequency, which showed a straight line, but with several anomalous results which I didn't pick up on when I plotted the first graph during the experiment, and had I done so, I would have taken repeats.

  1. Marked by a teacher

    Investigation:To find the refractive index of cooking oil.

    4 star(s)

    I think that cooking oil could be less dense than water because when it is put with water it separates and floats on top. However, it does look more physically dense than water does, as it has a more syrupy texture, so I think that it has a greater refractive index than water, but less than glass.

  2. refractive index prac report

    Over usage of light, reducing the strength of the light beam Improvements: There are some possible improvements that could be made to improve the results and practical experiment. The equipment should be checked prior to the practical to reduce errors during the experiment.

  1. To investigate how the depth of the water will effect the speed of a ...

    of the container altogether and so no energy is being lost and neither is it being gained so however much more liquid you put in from there the velocity of the wave will still remain the same.

  2. Find a relationship between the angles of incidence and the angles of refraction by ...

    the refracted angle increases beyond 90 degrees, the refracted ray is reflected back into the perspex, into the same plane as the incident angle. This phenomenon is called total internal reflection. This too can be calculated using Snell's law by setting the refraction angle equal to 90�.

  1. Deviation of Light by a Prism.

    Kaye and T.H.Laby") that I consulted to check if this value was correct gave an answer of 1.509. I have averaged the one obtained above and the one given by the data book to obtain a refractive index value for the glass I am using of 1.51.

  2. Investigating the speed of travelling waves in water.

    If the distance is too small, due to my reaction time, I may not have enough time to operate the stop clock appropriately. This would be especially hard when the speed of the waves increase, because they would travel the distance much faster, making it even tougher for me to time it.

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