CERTIFICATE
This is to certify that Nisha Borah of class XII-B of
science of Roll no. …………………… of Army Public
School Basistha has successfully completed and
submitted investigatory project entitled “To investigate the
dependence, of the angle of deviation on the angle of
incidence, using a hallow prism filled, one by one, with
different transparent fluids” to the department of physics
for AISSCE practical examination 2015-2016 as set by
Central Board of Secondary Education and it wholly
fulfilled the standard set by Central Board of Secondary
Education.
This project is absolutely genuine and does not
indulge any kind of plagiarism.
The reference taken in making this project has
been declared at the end of this project.
Signature of Principal
Teacher-in-charge
Mrs. Purnima Mehra
Kumar Jha
Signature of
Mr. Amarendra
(PGT)
Department of Physics
ACKNOWLEDGMENT
It is my proud privilege to offer my sincere
thanks to the Central Board of Secondary Education
who has given me this opportunity to make a project on
this subject successfully.
I would like to offer my sincere thanks and
gratitude to Madam Purnima Mehra, the principal of my
school to complete this in time.
I am extremely indebted to our physics teacher
Mr. Amarendra Kumar Jha for his able guidance,
timely help and constructive encouragements towards
the completion of this project.
And at last, I would like to offer my sincere
thanks to our lab assistance for guiding me on a step
by step basis and ensuring that I completed all my
experiments with ease.
PHYSICS
INVESTIGATORY
PROJECT
TOPIC: To investigate the dependence, of the angle of
deviation on the angle of incidence, using a hollow prism
filled, one by one, with different transparent fluids.
Submitted to the department of physics, Army Public School
Basistha for the fulfillment of AISSCE - 2015-2016, SCIENCE.
Submitted by:-
Nisha Borah
Class: XII-B
Roll no. –
INTRODUCTION
In optics, a prism is a transparent optical element
with flat, polished surfaces that refracts light. The exact
angles between the surfaces depend on the application.
The traditional geometrical shape is that of a triangular
prism with a triangular base and rectangular sides, and in
colloquial use “prism” usually refers to this type.
Some types of optical prism are not in fact in the
shape of geometric prisms. Prisms can be made from any
material that is transparent to the wavelengths for which
they are designed. Typical materials include glass, plastic
and fluorite. Prism can be used to break light up into its
constituent spectral colors (the colors of the rainbow).
Prisms can also be used to reflect light, or to split light into
components with different polarizations.
Before Isaac Newton, it was believed that white
light was colorless, and that the prism itself produced the
color. Newton’s experiments demonstrated that all the
colors already existed in the light in a heterogeneous
fashion, and that “corpuscles” (particles) of light were
fanned out
because particles with different colors traveled with
different speeds through the prism. It was only later that
Young and Fresnel combined Newton’s particle theory with
Huygens’ wave theory to show that color is the visible
manifestation of light’s wavelength. Newton arrived at his
conclusion by passing the red color from one prism
through second prism and found the color unchanged.
From this, he concluded that the colors must already be
present in the incoming light and white light consists of a
collection of colors. As the white light passes through the
triangular prism, the light separates into the collection of
colors: red, orange, yellow, green, blue, indigo and violet.
This collection of colors formed by the prism is called the
spectrum. The separation of white light into its spectrum is
known as dispersion.
Dispersion occurs because each color travels
through the prism at different speeds. Violet travels the
slowest through the prism; hence we can see it refracting
the most. On the other hand, red passes through at a
much fast rate which makes its angle of refraction less,
hence red is too scarce to be seen.
Experimental setup
AIM: To investigate the dependence, of the angle of
deviation on the angle of incidence, using a hallow
prism filled, one by one, with different transparent fluids.
APPARATUS:
Drawing board, white sheets of paper, hollow prism,
different liquids (water, kerosene oil, etc), drawing pins,
pencil, half meter scale, thump pins, graph papers and a
protractor.
THEORY:
Refraction of Light through a Prism –
Diagram shows section ABC of a prism taken by a
vertical plane, perpendicular to the edge. BC is the base
of the prism and AB and AC are its two refracting
surfaces.
DIAGRAM: Refraction through a prism.
RQ is the incident ray. QS
is the refracted ray. ST is
the emergent ray.
RQN1 = i = angle of incidence
SQN3 = r1 = angle of refraction inside prism
QSN3 = r2 = angle of incidence inside prism TSN2
= e = angle of emergence
BAC = A = angle of prism SFK =
D = angle of deviation
In
QFS, KFS =
FQS +
FSQ
D = (i – r1) + (e – r2)
D = i + e – (r1 + r2)
… (1)
In
QS1N3, r1 + r2 +
… (2)
QN3S = 180⁰
The quadrilateral AQN3S is cyclic quadrilateral, then A +
QN3S = 180
… (3)
From (2) and (3)
A = r1 + r2
… (4) Eq. (1) become
D = i + e -A
D+A=i+e
… (5)
Angle of Minimum Deviation Definition: The minimum value of angle of deviation is
called angle of minimum deviation. It is represented
by the symbol Dm.
Explanation: For same angle of deviation (D)
there are two values of angle of incidence. One value
equals ‘i’ and other value equals ‘e’.
As angle ‘i’ is increased from a small value, ‘e’
decreases from large value and angle of deviation
decreases. When angle of deviation is minimum
(Dm), then, ‘i’ and ‘e’ becomes equal.
The refracted ray QS goes parallel to base BC.
∵ n= sin i
sin r1
Since i = e, we have r1 = r2. (
=
sine
sinr 2
)
Hence, at minimum deviation, when r1 = r2 = r
(say).
We have
A = r1 + r2 = r + r = 2r
⇒
A
2
r=
Also, at minimum deviation, D = Dm and i =
e
From relation,
We have,
A+D=i+e
A + Dm = i + i = 2i
⇒
i=
A+Dm
2
From Snell’s law,
n=
We have
n=
sini
sinr
A + Dm
sin
2
A
sin
2
This relation is useful for determination of n for Prism
material.
DIAGRAM:
DIAGRAM: Refraction through prism at
different angles
PROCEDURE:
1.A white sheet of paper was fixed on the drawing
board with the help of drawing pins.
2. A straight line XX’ parallel to the length of the
paper was drawn nearly in the middle of the
paper.
3. Points Q1,Q2,Q3 and Q4 were marked on the
straight line XX’ at suitable distances of about 6cm.
4. Normal’s N1Q1,N2Q2,N3Q3 and N4Q4 were drawn
on points Q1,Q2,Q3 and Q4.
5. Straight lines R1Q1,R2Q2,R3Q3 and R4Q4 were
drawn making angles of 40⁰,45⁰,50⁰ and 55⁰
respectively with the normals.
6. One corner of the prism was marked as A and it
was taken as the edge of the prism for all the
observations.
7. Prism with its refracting face AB was put in the
line XX’ and point Q1 was put in the middle of AB.
8.The boundary of the prism was marked. 9.Two pins
P1 and P2 were fixed vertically on the
line R1Q1 and the distance between the pins were
about 2cm.
10. The images of points P1 and P2 were looked
through face AC.
11.Left eye was closed and right eye was opened
and was brought in line with the two
images.
12. Two pins P3 and P4 were fixed vertically at
about 2cm apart such that the open right eye sees
pins P4 and P3 as images of P2 and P1 in one
straight line.
13. Pins P1,P2,P3 and P4 were removed and their
pricks on the paper were encircled.
14.Steps 7 to 13 were again repeated with points
Q2,Q3 and Q4 for i=45⁰,50⁰ and 55⁰.
15. Straight lines through points P4 and P3 were
drawn to obtain emergent rays S1T1, S2T2, S3T3 and
S4T4.
16.T1S1,T2S2 ,T3S3 and T4S4 were produced inward in the
boundary of the prism to meet produced incident rays
R1Q1, R2Q2,R3Q3 and R4Q4 at points F1,F2,F3 and F4.
17. Angles K1F1S1,K2F2S2,K3F3S3 and K4F4S4 were
measured. These angles give angle of
deviation D1, D2,D3 and D4.
18. Values of these angles were written on the
paper.
19.Angle BAC was measured in the boundary of the
prism. This gives angle A.
20. Observations were recorded.
OBSERVATIONS:
Angle of hollow prism A = 60⁰
S.No.
1
2
3
4
Angle
of
incidenc
e
Angle of
deviatio
n for
water
40⁰
45⁰
50⁰
55⁰
23⁰
24⁰
25⁰
26⁰
Angle
of
deviatio
n for
kerosen
e oil
36⁰
33⁰
34⁰
35⁰
Angle of
deviatio
n for
turpenti
ne oil
32⁰
33⁰
34⁰
35⁰
RESULTS:
The angle of minimum deviation for– Water
Dm = 23⁰C
Kerosene oil Dm = 33⁰C
Turpentine oil Dm = 32⁰C
The refractive indices of theWater n = 1.32 Kerosene
oil n = 1.46 Turpentine oil
n = 1.44
Speed of light inWater v = 2.3x108 m/s Kerosene oil
v = 2.05x108 m/s Turpentine oil v =
2.08x108 m/s
PRECAUTIONS:
 The angle of incidence should lie between 35⁰
– 60⁰.
 The pins should be fixed vertical.
 The distance between the two pins should not
be less than 10mm.
 Arrow heads should be marked to represent the
incident and emergent rays.
 The same angle of prism should be used for all
the observations.
SOURCES OF ERRORS:
 Pin pricks may be thick.
 Measurement of angles may be wrong.
BIBLIOGrAPHY
The following sources were used for the appropriate
information required to complete the project:
Comprehensive: Practical Physics Class XII
NCERT textbook of class XII
Google
CONTENTS
Introduction
Experimental setup
Bibliography
CONTENTS
Introduction
Experimental setup
Bibliography