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In this experiment, a mechanism is prepared to observe the refraction of light and calculate refractive index of water

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Introduction

REFRACTION OF LIGHT

CANDIDATE’S NAME:

BAŞAK BAYRAMBAŞ

INSTRUCTOR’S NAME:

MİNE GÖKÇE ŞAHİN

PARTNER’S NAME:

BATU AYTEMİZ

CRITERIA TO BE EVALUATED:

Data Collection & Processing, Conclusion & Evaluation

INTRODUCTION

        In this experiment, a mechanism is prepared to observe the refraction of light and calculate refractive index of water according to the data taken from the experiment.

Refraction means the bending of a wave resulting from a change in its velocity as its moves from one medium to another. Since the frequency of a wave cannot change, independent of the source changing its frequency when it originally emits a wave. This change in wave velocity must result from a change in its wavelength in the second medium.[1]

image30.gif

As shown in the diagram, when the waves encounter an oblique interface, both their direction and wavelength change. In the instance illustrated, the wavelengths shorten and the reflected rays “bend toward the normal” as the wave enter the shallow or slower medium: image00.png

To quantify the degree of refraction, a dimensionless quantity called index of refraction (n) is introduced.

n=c/v

where;

c: speed of light in a vacuum

v: average speed of light in the optically dense medium

n: medium’s index of refraction

Some common indices of refraction for a midrange wavelength of light (589 nm, a prominent line in the emission spectrum of sodium) are:

vacuum

1.00000

fused quartz

1.46

air (STP)

1.00029

crown glass

1.52

water (20ºC)

1.33

polystyrene

1.55

acetone

1.36

carbon disulfide

1.63

ethyl alcohol

1.36

flint glass (heavy)

1.65

sugar solution (30%)

1.38

sapphire

1.77

sugar solution (80%)

1.49

diamond

2.42

As it is shown in the table above refractive index of matters are constant.

DATA COLLECTION & PROCESSING

Trials

θ (Air)(±1.0)

θ (Water)(±1.0)

0

0.0

0.0

1

18.0

13.0

2

19.5

15.0

3

30.0

23.0

4

33.5

25.0

5

46.0

32.0

6

50.0

35.0

7

65.0

43.0

...read more.

Middle

4

0.55

0.42

0.01

0.02

5

0.71

0.52

0.01

0.01

6

0.76

0.57

0.01

0.01

7

0.90

0.68

0.01

0.01

Table 2: Sine of angles of light with y-axis in medium of air and water for each trial

Uncertainty calculation of sine of angles which are shown above in Table 2:

image01.png

For Trial 1:image02.png

Snell’s Law:

When the light passes from one transparent medium to another, it bend according to Snell’s law which states that;[2]

image03.png

  • n: refractive index (optical density) of the medium

sinimage04.png

  • : sine of the angle with y-axis

image05.png

image06.png

image07.png

image08.png

        Since the refractive index (optical density) of air is equal to 1 (image09.png

, refractine index of water image10.png

 is equal to sine of angle of light in medium of air (image11.png

 over sine of angle of light in medium of water (image12.png

.

image13.png

        That’s why slope of the graph image14.png

 vs image15.png

 gives the approximate value of refractive index of water image10.png

.

Figure : Graph of image14.png

 vs image15.png

image31.png

        Since image14.png

 is proportional to image15.png

, the graph which is given above is linear.

        According to the graph above, slope of best fit line gives the experimental value of refractive index of water, slope of worst line with greatest slope gives the maximum value of refractive index of water and the worst line with least slope gives the minimum value of refractive index of water in this experiment.

image16.png

Uncertainty of refractive index of water image17.png

:

image18.png

image19.png

Percentage error calculations:

image20.png

CONCLUSION & EVALUATION

        In this experiment, refractive index or in other words optical density of water (image21.png

 is aimed to be found by the help of parallax method.

...read more.

Conclusion

laboratory or field devices for the measurement of an index of refraction usually takes measurement for standard temperature (298.15K/25°C).[7] That’s why, making experiment at standard temperature gives better results. Moreover, refractive index of vacuum which is a measurement of standard temperature is taken used during the calculations. Therefore, during the experiment paying attention to the temperature and trying to make it constant at 25°C makes the results better.

        Another limitation is the thickness of the needles. Using thick needles can be misleading for the results of the experiment by affecting observations of refraction. So, thinner needles can solve that error source.

WORKS CITED PAGE

  1. http://dev.physicslab.org/Document.aspx?doctype=3&filename=GeometricOptics_refractionLight.xml
  2. http://interactagram.com/physics/optics/refraction/
  3. http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/Physics/refractionsnells.htm
  4. Giancoli, physics, sixth edition, Pearson Education International
  5. http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html
  6. http://www.physicsclassroom.com/class/refrn/u14l1d.cfm
  7. http://webapps-new.utsc.utoronto.ca/chemistryonline/refractive.html

[1]http://dev.physicslab.org/Document.aspx?doctype=3&filename=GeometricOptics_refractionLight.xml

[2]http://interactagram.com/physics/optics/refraction/

[3]http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/Physics/refractionsnells.htm

[4] Giancoli, physics, sixth edition, Pearson Education International

[5]http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html

[6]http://www.physicsclassroom.com/class/refrn/u14l1d.cfm

[7]http://webapps-new.utsc.utoronto.ca/chemistryonline/refractive.html

...read more.

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