Physics lab presentation

1. Measuring the
Refractive Index of
Prism Material Using a
Spectrometer
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presentation begins!
ANTLIA
ORION
1998
1998

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TABLEOFCONTENTS
01.
OVERVIEW
02.
FEATURES OFTHETOPIC
03.
Experimental Data
04.
Discussion &
Conclusion
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3. INTRODUCTION
The refractive index of a material isa fundamental
property that describes how much the speed of
light is reduced as it passes through the material.
Measuring the refractive index of a material is
essential in designing and analyzing optical
instruments such as lenses, prisms, and fibers. In
this experiment, we will determine the refractive
index of the material of a prism using a
spectrometer
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01.

4. REFRACTIVEINDEX
Refractive index is a fundamental property of a material that
describes how much the speed of light is reduced as it passes
through the material compared to the speed of light in a
vacuum
02.
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WHATANGLEOFDEVIATION?
When a rayof light enters a prism, it undergoes
refraction, orbending, due to the change in the
speed of light as it passes from one medium (air) to
another (the prism material). The angle of deviation
is the angle between the incident ray and the
emergent ray after passing through the prism. It
represents the amount by which the direction of the
light ray changes as a result of refraction in the
prism
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WHATANGLEOFDEVIATIONINPRISM?
AprismwithaprismangleAis to beconsidered.ArayofOP isto be
allowedtostrikethe
firstfaceofaprism,whichpassesthroughthe prism’sprimaryplane,
and emergesfromthe
otherfacein the directionQR.Let i1and r1bethe incidenceand
refractionangles onthe
prism'sfirstface,andi2 &r2bethe correspondingvariablesonthe
prism'ssecondface.
Whenthe angles i1= i2 andr1=r2, the positionofminimumdeviationis
achievedasthe ray
passessymmetricallythroughtheprism.
Weknowthe angleof prism,A= r1+ r2
Inthe positionofminimumdeviation,
A= 2r1
Or,r1= A/2
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ANGLEOFDEVIATIONINPRISM
Now,the deviationofthe ray,
δ = (i1– r1)+ (i2-r2)
Or,δ = (i1+ i2) + (r1+ r2)
Or,δ = (i1+ i2) – A
Inthepositionofminimumdeviation,
δ = δm
δm= 2i1-A
Or,i1 = 𝜹𝒎 +𝑨/𝟐
FromSnell’sLaw,the refractiveindex,
µ= 𝑺𝒊𝒏𝒊𝟏/𝑺𝒊𝒏𝒓𝟏
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µ =
𝑺𝒊𝒏 (𝜹𝒎 +𝑨)/2
‫𝑨ܖܑܛ‬/2

8. Apparatus
Sodium lamp
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Spectrometer
Prism
Stopwatch

9. Experimental procedure
Adjustment of Telescope:
a. The spectrometer and the prism table were arranged in
horizontal position and levelling screws were used to tighten
it.
b. A clear and sharp image was received as the telescope
was turned towards a distant object.
c. The slit was illuminated by a sodium vapor lamp. The slit
and the collimator were suitably adjusted, such that, a narrow
& vertical image of the slit was received.
d. The telescope was turned such that it received a direct ray
which coincided with the vertical crosswire
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Figure: Arrangement to determine angle of minimum deviation

10. Experimental procedure
Measurement of angle of minimum deviation:
a. A prism was placed such that the center of the prism
coincided with the center of the prism table, the incident
ray fell on one of the polished faces and the refracted ray
emerged out of the other polished face. The telescope
was turned such that the refracted image could be viewed
on the other face. Figure 2: Spectrometer
b. The Vernier table was slowly turned in a direction such
that the image of the slit moved towards the directed ray,
i.e., it moved in the direction which the angle of deviation
decreased.
c. The image was found to be stationary at a certain
position. The Vernier table was fixed to that position. The
telescope and the fine adjusting slider were used so that
the slit coincided with the cross wire.
d. The corresponding main scale and both the Vernier
scales (Vernier I and Vernier II) readings were noted.
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e. The prism was carefully removed from the prism table. The
telescope was turned parallel to the collimator and the direct ray
readings were noted.
f. The difference between the direct ray readings and the deviated
readings were found, which was the angle of minimum deviation,
𝜹𝒎 . The refractive index of the material of the prism was found
through use of equation 1.

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03.

12. Analysis andCalculation
Reflective Index, µ =
𝑺𝒊𝒏(𝜹𝒎+𝑨)/2
‫𝑨ܖܑܛ‬/2
µ =
𝑺𝒊𝒏 (38.215 +60)/2
‫ܖܑܛ‬60/2
µ = 1.5118
Therefore, given prism is a flint prism with theoretical refractive index, µ= 1.5118
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13. Discussion
•Importance of refractive index: The refractive index is a
fundamental property of a material that affects how light
interacts with it. Measuring the refractive index is
important for designing and analyzing optical systems
such as lenses, prisms, and fibers.
•Principles of the experiment: The experiment involves
measuring the angle of deviation of a light ray passing
through a prism using a spectrometer. By knowing the
geometry of the prism and the angle of deviation, we
can calculate the refractive index of the prism material
using Snell's law.
•Materials and equipment: To conduct the experiment,
we need a prism, spectrometer, light source, ruler, and
protractor. The prism should be made of a material with
a known refractive index.
•Experimental procedure: The experimental procedure
involves setting up the spectrometer, aligning the prism,
measuring the angle of deviation, and calculating the
refractive index. The angle of deviation is the angle
between the incident ray and the emergent ray after
passing through the prism.
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The refractive index is calculated by using Snell's law,
which relates the angle of incidence and angle of
refraction to the refractive indices of the two media.
•Source of error: There are several sources of error
that can affect the accuracy of the experiment,
such as imperfections in the prism, misalignment of
the spectrometer, and variations in the wavelength
of the light source.
•Applications: The experiment has practical
applications in the field of optics and photonics,
where the refractive index is a crucial parameter in
the design of optical devices such as lenses,
prisms, and fibers. Knowledge of the refractive
index can also help in the identification and
characterization of materials.
Overall, this experiment provides a hands-on
demonstration of the principles of optics and helps to
reinforce the concepts of refraction, Snell's law, and
the geometry of optical systems
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14. CREDITS: This presentation template was created
by Slidesgo, including icons by Flaticon, and
infographics & images by Freepik
THANKYOU
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