• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12
  13. 13
    13

Deviation of Light by a Prism.

Extracts from this document...

Introduction

Nigel Evans

Physics Coursework – “Deviation of Light by a Prism”

        -  -

Deviation of Light by a Prism

Aim

The aim of this investigation is to test using a prism how the angle of deviation (how far the light ray is deviated from its original position) is affected by varying the angle of incidence (where the light ray goes into the prism), and whether this has any relation to the angle of emergence (where the light actually comes out of the prism).

Planning

I firstly need to conduct theoretical work and a preliminary investigation to test what is going on and to get a clearer view of the aspects of the investigation. In my theoretical work I will have to use the geometry of triangles and Snells Law. For Snells law to work, I will need to know the refractive index of the glass that I am using. To do this I will use a glass block of the same glass as the prism, and then use sighting pins (and light) to pinpoint the incident ray and the emergence ray and then find the angle of refraction. A more detailed description of how this experiment is going to work can be seen below.

To find the refractive index of the glass that I will be using in the actual experiment, I set up a glass block that was of the same type of glass as the prism, and lined up sighting pins through it. This enables me to draw the angle of incidence (measured from the Normal (dotted line below), a line at 90° to where the incident ray strikes the glass block) and this also enables me to draw the angle of emergence (where the light exits the prism).

...read more.

Middle

Sin R2 x n = Sin E

Sin 29.5° x 1.51 = 0.744

Sin-1 0.744 = 48.1°

Therefore E = 48.1°

Now that I have all for values need to calculate the deviance I again have to use the fact that X + Y = δ:

(I – R1) + (E – R2) = δ

(50 – 30.5) + (48.1 – 29.5) = δ

19.5 +18.6= 38.1°

Below is a results table of the answers that I have gained for the angles sizes using the two above methods.

Results Table for Theoretical Modelling:

Incident Ray, I (°)

Refracted Ray, R1 (°)

Refracted Ray, R2 (°)

Emergence Ray, E (°)

Deviation, δ (°)

20

13.0913

46.9087

Not Possible

Not Possible

25

16.2530

43.7470

Not Possible

Not Possible

30

19.3371

40.6629

79.71

49.71

35

22.3245

37.6755

67.35

42.35

40

25.1942

34.8058

59.53

39.53

45

27.9229

32.0771

53.31

38.31

50

30.4851

29.5149

48.06

38.06

55

32.8530

27.1470

43.55

38.55

60

34.9965

25.0035

39.66

39.66

65

36.8845

23.1155

36.36

41.36

70

38.4852

21.5148

33.63

43.63

75

39.7684

20.2316

31.48

46.48

80

40.7070

19.2930

29.93

49.93

85

41.2794

18.7206

28.99

53.99

90

41.4718

18.5282

28.67

58.67

These are the calculated values for the prism, using the refractive index for the glass as 1.51. Any values before 30° are not possible because the refracted ray will appear at the wrong side of the prism. This factor makes the SINE of the angle bigger that 1 and therefore it is not possible to calculate a value for the emergence ray and also therefore not for the deviance either (as there is no emergence ray to calculate it from). The Incidence angle of 90° is also highlighted because although this value and other values above it are possible in calculation in practice the 90° angle would actually miss the prism and the values of the incidence ray above 90° would have to come from inside the prism itself. I have therefore chosen to take readings in the range of 30° - 85°. I will take one reading below 30° but this will only be taken to prove right my initial theory work and will not be taken into consideration in any conclusions that I draw.

Over the next two pages is two graphs plotted in the incident angle range of 30° - 85°, which show the predicted trend in

...read more.

Conclusion

I would also maintain a sharper pencil at all times as this would make angle measuring easier, and maintain a high degree of accuracy in my investigation.

I would try and obtain a angle measuring tool that is of a better standard that a protractor and measures to a higher degree of accuracy, to ensure that all my results were very reliable.

Reliability

Overall I think my results were very reliable, and they linked back very well to my initial calculations. I think there is room for improvement as there is in any case but overall I think that my investigation was conducted reliably and to as high a degree of accuracy as the involved apparatus permitted.

Anomalous results

There were no major anomalies in my results, but having said this the two graphs that I have prepared from my results show some points that do not fit the exact trend, but they are still acceptable. An example of this is on the graph of the angle of emergence plotted against the angle of incidence, the two values of incidence angles 35° and 60° show slight bumps, even thought he line should be a perfect curve. These two could have arisen to inaccuracy on my part or for one of the reasons stated in the above sections.

The second graph of angles of deviation plotted against the angles of incidence show no real anomalous results with all points fitting the general trend of the graph in the same way that my initial calculations did (i.e. a smooth curve).

To conclude I think that given the situation and the equipment provided, I made the best use of it and even through there was room for improvement, my collected results were of a high standard as shown when comparing to my calculated values.

...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)

    These results may not be exact, but a rough guide, which will help to predict the refractive index for oil. I will use the following method for the pilot experiment. 1. Prepare the required apparatus 2. On the piece of paper place the empty plastic tray and draw round the base of the tray.

  2. Marked by a teacher

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

    4 star(s)

    I will take this range as I predict that in-between 400 - 450 will be the critical angle.

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

    * Be careful of electricity Method: 1) Mark and label points with a light pencil, of the various angles to be measured. (Use a protractor) 2) Place the semicircular perspex block within the contours of the semicircle drawn on the grid provided.

  2. An Investigation into the Effect on the Critical Angle by Changing the Colour of ...

    * The colour of the light:- different colours of light have different wave lengths, this correlates to their position in the electromagnetic spectrum with red light having the longest wavelength and violet light having the shortest wavelength. This factor makes a difference to the critical angle because the higher the

  1. Refractrometry. Aim: Using a model Pulfrich refractometer determine the refractive index of a range ...

    Using your eye at the level of the block on the desk move your eye from left to right until you determine the exact point the black paper disappears from sight. 6. Without moving your eye, place a pin next to block in line with your sight of disappearance.

  2. Carry out an experiment to find a relationship between the incident angle and the ...

    When the light is shone at the Perspex at an angle of 0 � There will not be a change to the direction of light, as each edge of the light slows down at the same point, keeping the light in a straight line.

  1. Find the relationship between the angle of incidence and angle of refraction for light ...

    air and as soon as it touches the block it enters the glass, which is said to be another medium. Glass is said to be a shallower material and therefore when the light enters the medium its direction changes and the speed is reduced.

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

    We see all other things because light from a source bounces off them and travels to us. Light sources can be classified as natural or artificial. Natural light comes from sources that we do not control. Such sources include the sun and the stars.

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