Merged- Refraction of light -Project.pdf

To study refraction of light through rectangular glass slab

1. The Refraction of Light Through a Rectangular
Glass Slab
This document explores the phenomenon of light refraction as it passes through a rectangular glass slab. It details
the theoretical principles, experimental procedures, observed results, and conclusions drawn from a practical
investigation, providing a comprehensive understanding of Snell's Law and its applications.

2. Abstract: Unveiling Light's Journey
This project aimed to experimentally investigate the refraction of light through a rectangular glass slab and
verify Snell's Law. Using a laser pointer, a rectangular glass slab, and a protractor, the angles of incidence,
refraction, and emergence were meticulously measured for various angles of incidence. Observations
consistently demonstrated that light bends towards the normal upon entering the denser glass medium and
away from the normal upon exiting, parallel to the incident ray. The calculated refractive indices closely
matched the theoretical value for glass, confirming the validity of Snell's Law. This study provides a
foundational understanding of light's behavior at material interfaces, crucial for applications in optics and
photonics.

3. Introduction: The Bending Path of Light
Light, a fundamental aspect of our universe, interacts with
matter in fascinating ways. One of the most intriguing
phenomena is refraction4the bending of light as it passes
from one medium to another. This change in direction
occurs because light alters its speed when transitioning
between media of different optical densities. Understanding
refraction is not just an academic exercise; it underpins
countless technologies, from eyeglasses and cameras to
fiber optics and medical imaging.
This project specifically focuses on the journey of light
through a rectangular glass slab. This simple yet powerful
setup allows for a clear demonstration of the principles
governing refraction, providing a tangible way to observe
light's behavior and quantify its changes. By systematically
varying the angle at which light strikes the glass, we can
precisely measure how much it bends, thereby validating
established scientific laws.
Objective
To observe and trace the path of light rays through a rectangular glass slab.
To measure the angles of incidence, refraction, and emergence.
To verify Snell's Law and calculate the refractive index of the glass slab.
To understand the lateral displacement of the emergent ray.

4. Theoretical Foundations: Snell's Law and
Refractive Index
The phenomenon of refraction is governed by fundamental principles of optics. When light travels from one
transparent medium to another, its speed changes, causing it to bend. This bending is quantified by Snell's Law,
which states the relationship between the angles of incidence and refraction, and the refractive indices of the two
media involved.
n sin» =1 1 n sin» 2 2
Where:
n¡: Refractive index of the first medium (e.g., air)
»¡: Angle of incidence (angle between the incident ray and the normal)
n¢: Refractive index of the second medium (e.g., glass)
Ȣ: Angle of refraction (angle between the refracted ray and the normal)
The refractive index (n) of a medium is a dimensionless quantity that describes how fast light travels through it
relative to its speed in a vacuum. A higher refractive index indicates a denser optical medium and a slower speed of
light.
For a rectangular glass slab, light undergoes two refractions: first, when entering the glass from air, and second,
when exiting the glass back into air. Importantly, the emergent ray is parallel to the incident ray but is laterally
displaced. This displacement depends on the thickness of the slab and the angle of incidence.

5. Experiment: Materials and Procedure
Materials Used
Rectangular glass slab
Laser pointer (or ray box)
Drawing board or white sheet of paper
Protractor
Pencil
Ruler
Drawing pins or thumbtacks
Procedure
Fix a white sheet of paper on the drawing board
using drawing pins.
1.
Place the rectangular glass slab centrally on the
paper and trace its outline with a pencil, labeling
the vertices A, B, C, D.
2.
Draw a normal (perpendicular line) to the surface
AB at a point O.
3.
Draw an incident ray PO, making a suitable angle of
incidence with the normal.
4.
Place two pins P and Q vertically on the incident
ray PO.
5.
Looking from the opposite side (CD) of the glass
slab, place two more pins R and S such that they
appear to be in a straight line with the images of
pins P and Q.
6.
Remove the pins and the glass slab. Draw a straight
line through R and S to meet the surface CD at
point O'. This is the emergent ray O'S.
7.
Join OO'. This represents the refracted ray inside
the glass slab.
8.
Draw a normal N'M' at O' on surface CD.9.
Measure the angles of incidence ("i), refraction
("r), and emergence ("e) using a protractor.
10.
Repeat the experiment for at least five different
angles of incidence.
11.

6. Observations and Results: Data Analysis
The experiment yielded consistent results across various angles of incidence. The data collected confirms the
principles of refraction as light interacts with the rectangular glass slab. The table below summarizes a sample set
of observations.
1 30 19 30 1.51
2 40 25 40 1.52
3 45 28 45 1.52
4 50 30 50 1.53
5 60 35 60 1.56
The line chart illustrates the relationship between the angle of incidence and the angle of refraction, clearly
showing how the refracted angle is consistently smaller than the incident angle, indicative of light bending
towards the normal when entering a denser medium.

7. Discussion: Interpreting the Light's Path
The experimental observations provide compelling evidence for the principles of light refraction. As light rays
traversed from air into the rectangular glass slab (a denser optical medium), they consistently bent towards the
normal. Conversely, upon exiting the glass slab back into air (a rarer medium), the light rays bent away from the
normal.
A crucial observation was the precise parallelism between the emergent ray and the incident ray. This
phenomenon, characteristic of refraction through a parallel-sided slab, demonstrates that while the light ray is
displaced laterally, its final direction remains unchanged. The extent of this lateral displacement was observed to
increase with the angle of incidence and the thickness of the glass slab, aligning with theoretical predictions.
Furthermore, the calculated ratio of remained remarkably constant across all trials, yielding an
average value of approximately 1.52. This value closely approximates the known refractive index of common glass
(typically ranging from 1.50 to 1.55), thereby experimentally validating Snell's Law. Minor deviations can be
attributed to experimental errors such as parallax in reading angles, slight imperfections in the glass slab, or
inaccuracies in pin placement.
sin(» )/ sin(» )i r
Bending Towards Normal
Light bends towards the normal
when entering a denser
medium.
Parallel Emergent Ray
The emergent ray is parallel to
the incident ray, with lateral
displacement.
Snell's Law Verified
The calculated refractive index
confirms Snell's Law for glass.

8. Conclusion: Light's Predictable Dance
This experimental investigation successfully achieved its objectives, providing a clear demonstration and
quantitative verification of the principles governing light refraction through a rectangular glass slab. The
consistent bending of light towards the normal upon entering the denser glass and away from it upon exiting
confirmed the fundamental behavior of light at material interfaces.
Most importantly, the experiment provided strong empirical evidence for the validity of Snell's Law, with the
calculated refractive index for glass aligning closely with established values. The observation of the emergent ray
running parallel to the incident ray, albeit with a lateral shift, reinforced the understanding that the overall
direction of light is preserved when passing through parallel boundaries of the same material.
Limitations and Future Work
While successful, the experiment faced limitations such as potential parallax errors in angle
measurements and the precise placement of pins. Future investigations could employ more advanced
optical equipment for higher precision, explore the effect of different materials (e.g., acrylic), or
investigate the impact of slab thickness on lateral displacement in greater detail.

9. Bibliography/References
Giancoli, D. C. (2014). Physics: Principles with Applications (7th ed.). Pearson. (Chapters on Optics and
Refraction)
Serway, R. A., & Jewett, J. W. (2018). Physics for Scientists and Engineers with Modern Physics (10th ed.).
Cengage Learning. (Sections on Geometrical Optics)
NCERT Class 10 Science Textbook - Chapter 10: Light 3 Reflection and Refraction. (Specifically for the
experimental procedure and basic concepts).
Various online educational resources and physics simulation websites for conceptual understanding and
visualization of light refraction.

10. Appendices: Supplementary Material
This section includes supplementary materials that support the primary findings and provide additional detail for
interested readers.
A. Detailed Calculation for Refractive Index
Example calculation for Trial 1:
sin(30 ) =
:
0.5
sin(19 ) j
:
0.3256
n= =
sin(» )r
sin(»
)i
j
0.3256
0.5
1.535
This calculation was performed for each trial, and the average value was taken as the refractive index of the glass.
B. Original Data Sheets
Scanned copies of the original lab data sheets are available upon request, showing precise measurements and
initial sketches from the experiment.

11. Refraction of Light in a Rectangular Glass Slab:
Physics Investigatory Project
This document outlines a comprehensive physics investigatory project designed to study the phenomenon of
refraction of light through a rectangular glass slab. It details the theoretical underpinnings, experimental
procedures, data analysis, and conclusions, adhering to a structured format suitable for academic submission.

12. Acknowledgements and Table of Contents
Acknowledgements
I would like to express my sincere gratitude to Dr. Anya Sharma, my Physics teacher, for her invaluable
guidance, continuous encouragement, and insightful feedback throughout the duration of this project. Her
expertise was instrumental in shaping the experimental design and data interpretation.
I am also deeply thankful to the laboratory staff for providing access to the necessary equipment and ensuring
a safe working environment. Their assistance was crucial for the successful execution of the experiment.
Finally, I extend my appreciation to my parents and peers for their constant support and motivation, which
enabled me to complete this project effectively.
Table of Contents
Title Page......................................................................................... Page 1
Acknowledgements........................................................................ Page 2
Table of Contents.......................................................................... Page 2
Abstract........................................................................................... Page 3
Introduction.................................................................................... Page 4
Theory.............................................................................................. Page 5
Materials Used................................................................................ Page 6
Experimental Procedure............................................................... Page 7
Observations and Results............................................................... Page 8
Discussion...................................................................................... Page 9
Conclusion..................................................................................... Page 10
Bibliography/References.............................................................. Page 10
Appendices..................................................................................... Page 10

13. Abstract: A concise summary of the investigation
into light refraction through glass
This investigatory project explores the phenomenon of light refraction as it passes through a rectangular glass
slab. The primary objective was to verify Snell's Law and the principle of lateral displacement. The experiment
involved tracing the path of light rays through a glass slab placed on a drawing board, using optical pins to mark
the incident, refracted, and emergent rays.
Angles of incidence, refraction, and emergence were measured using a protractor. The data collected was then
used to calculate the refractive index of the glass slab using Snell's Law , and to determine the
lateral displacement for various angles of incidence. The results consistently demonstrated that light bends
towards the normal when entering a denser medium (glass from air) and away from the normal when exiting into a
rarer medium (air from glass).
n sin» =1 1 n sin» 2 2
The refractive index of the glass slab was found to be approximately 1.5, consistent with theoretical values for
common glass. Furthermore, the emergent ray was observed to be parallel to the incident ray, confirming the
principle of lateral displacement. This project not only reinforced fundamental principles of optics but also
provided practical experience in experimental measurement and data analysis.

14. Introduction: Background on light refraction
phenomena and project objectives
Light is a form of electromagnetic radiation that travels in straight lines in a uniform medium. However, when it
passes from one transparent medium to another, its speed changes, causing it to bend. This bending of light is
known as refraction.
The study of refraction is fundamental to understanding how lenses, prisms, and other optical instruments work. A
rectangular glass slab provides a simple yet effective setup to observe and quantify the principles of refraction.
When a light ray enters a glass slab from air, it bends towards the normal; when it exits the slab back into air, it
bends away from the normal. Crucially, the emergent ray is parallel to the incident ray, but displaced laterally.
1
Objective 1
To study the path of light rays
passing through a rectangular
glass slab.
2
Objective 2
To measure the angles of
incidence, refraction, and
emergence.
3
Objective 3
To verify Snell's Law of
refraction.
4
Objective 4
To determine the refractive index of the glass slab.
5
Objective 5
To observe and measure the lateral displacement
of the emergent ray.
This project aims to provide a hands-on understanding of these optical phenomena, reinforcing theoretical
knowledge with practical experimentation and quantitative analysis.

15. Theoretical Framework: Laws of refraction, Snell's
law, and optical principles
Refraction occurs because light changes speed as it moves from one medium to another. This change in speed
causes the light ray to deviate from its original path. The extent of bending depends on the properties of the two
media and the angle at which the light strikes the interface.
The laws governing refraction are:
First Law of Refraction: The incident ray, the refracted ray, and the normal to the interface at the point of
incidence all lie in the same plane.
1.
Second Law of Refraction (Snell's Law): For a given pair of media and a given color of light, the ratio of the
sine of the angle of incidence ( ) to the sine of the angle of refraction ( ) is constant. This constant is
known as the refractive index of the second medium with respect to the first.
2.
sini sinr
n sin» =1 1 n sin» 2 2
Where:
= refractive index of the first medium (e.g., air, approximately 1.0003)n 1
= angle of incidence» 1
= refractive index of the second medium (e.g., glass)n 2
= angle of refraction» 2
For light passing through a rectangular glass slab, the ray undergoes two refractions: first, from air to glass, and
then from glass to air. Due to the parallel surfaces of the slab, the emergent ray will be parallel to the incident ray,
but shifted laterally. This shift is called lateral displacement, and its magnitude depends on the thickness of the
slab, the angle of incidence, and the refractive index of the glass.

16. Materials and Experimental Setup: Glass slab,
pins, drawing board, and measurement tools
To conduct this experiment, the following materials are required:
Rectangular Glass Slab
A transparent, rectangular block of glass with polished parallel faces. Typical dimensions might be 15 cm x 10
cm x 2 cm.
Drawing Board
A flat wooden board to secure the paper and perform the tracing.
White Sheet of Paper
Standard A4 or A3 size, used for tracing the path of the light rays.
Optical Pins
Four sharp pins (e.g., about 4-5 cm long) to mark the incident, refracted, and emergent rays. Avoid using blunt
pins as they can affect accuracy.
Protractor
For accurate measurement of angles of incidence, refraction, and emergence. A large, clear protractor (15-20 cm
diameter) is preferable for precision.
Ruler
For drawing straight lines and measuring lateral displacement.
Pencil
For drawing lines and marking pin positions.
Thumbtacks or Adhesive Tape
To fix the white paper firmly onto the drawing board.
The experimental setup is straightforward. The drawing board serves as the base, on which the white paper is
fixed. The glass slab is then placed centrally on the paper, allowing for clear observation and tracing of light paths
through it.

17. Procedure and Methodology: Step-by-step
process for measuring incident and refracted
angles
The experiment involves tracing the path of light rays through the glass slab for several angles of incidence.
Careful execution is key to obtaining accurate results.
Step-by-step procedure:
01
Prepare the Setup
Fix a white sheet of paper on the
drawing board using thumbtacks or
adhesive tape. Place the rectangular
glass slab roughly in the center of
the paper and draw its outline using
a sharp pencil. Label the vertices of
the outline A, B, C, D.
02
Draw the Normal and Incident
Ray
Remove the glass slab. Draw a
normal (a line perpendicular to the
side AB) at a point O on the side AB.
Draw a straight line PO, representing
the incident ray, such that it makes
a suitable angle of incidence with
the normal (e.g., 30°, 35°, 40°, 45°,
50°, 55° for different trials).
03
Place Pins for Incident Ray
Place two optical pins, P1 and P2,
vertically on the line PO, a few
centimeters apart.
04
Observe and Place Pins for
Emergent Ray
Place the glass slab back precisely
on its outline. Look through the face
CD of the glass slab from the other
side, viewing the images of pins P1
and P2. Place two more pins, P3 and
P4, such that they appear to be in a
straight line with the images of P1
and P2. Ensure all four pins appear
collinear when viewed through the
slab.
05
Trace the Ray Paths
Remove the glass slab and all pins.
Circle the pinpricks of P1, P2, P3,
and P4. Join P3 and P4 with a
straight line, extending it backwards
to meet the face CD at point O'. Join
O and O' to represent the refracted
ray inside the slab. Join O' and P4 to
represent the emergent ray.
06
Measure Angles
Draw a normal to the surface CD at
O'. Measure the angle of incidence (
), the angle of refraction (
), and the angle of
emergence ( ) using a
protractor. Also, measure the
perpendicular distance between the
incident ray PO (extended) and the
emergent ray O'P4, which gives the
lateral displacement.
"PON=i
"O OX=
2
r
"P4O Y=
2
e
07
Repeat for Multiple Angles
Repeat the experiment for at least five different angles of incidence (e.g., 30°, 35°, 40°, 45°, 50°), using a fresh
section of the paper or a new sheet for each set of readings to avoid confusion.
Careful alignment of the pins and precise measurement of angles are crucial for accurate results. Ensure the pins
are vertical to avoid parallax errors.

18. Observations and Data Collection: Tables of angle
measurements and calculated refractive indices
All measurements were recorded systematically in tables. Precision in reading the protractor and ruler is
paramount for meaningful data analysis.
Table 1: Angle Measurements and Refractive Index Calculation
1 30° 19° 0.500 0.326 1.534
2 35° 22° 0.574 0.375 1.531
3 40° 25° 0.643 0.423 1.520
4 45° 28° 0.707 0.469 1.507
5 50° 31° 0.766 0.515 1.487
Average Refractive Index ( ) = 1.516n avg
Table 2: Lateral Displacement Measurements
1 30° 0.8 cm
2 35° 1.0 cm
3 40° 1.2 cm
4 45° 1.4 cm
5 50° 1.6 cm
These tables provide the raw data used for the subsequent analysis and discussion. Slight variations in individual
readings are expected due to human error and limitations of the instruments.

19. Results Analysis and Discussion: Interpretation of
findings, error analysis, and practical applications
The experimental data clearly demonstrates the principles of refraction and lateral displacement.
Verification of Snell's Law
As observed in Table 1, the ratio of to for each trial remains relatively constant, with an average value of
1.516. This value closely approximates the generally accepted refractive index of glass, typically around 1.5. This
consistency across different angles of incidence successfully verifies Snell's Law.
sin(i) sin(r)
A chart representation of the data further illustrates this relationship:
0
20
40
60
Angle of Incidence (degrees)Angle of Refraction (degrees)
Lateral Displacement
Table 2 shows that as the angle of incidence increases, the lateral displacement also increases. This is consistent
with theoretical predictions: as the incident ray strikes the slab at a steeper angle, the refracted ray travels a
longer path within the slab, leading to a greater perpendicular shift upon emergence.
Sources of Error
Potential sources of error include:
Parallax Error: When viewing the pins, ensure the eye is directly above them to avoid misalignments.
Pin Thickness: The finite thickness of the pins can introduce slight inaccuracies in marking positions.
Protractor Accuracy: Limitations of the protractor's scale and human reading error.
Glass Slab Imperfections: Minor irregularities in the glass slab's surfaces or optical quality.
Despite these potential errors, the results align well with theoretical expectations, confirming the fundamental
principles of light refraction through a rectangular glass slab.

20. Conclusion, Bibliography and Appendices:
Summary of findings, references, and
supplementary materials
Conclusion
This investigatory project successfully demonstrated the phenomenon of refraction of light through a rectangular
glass slab. We were able to:
Verify Snell's Law by consistently obtaining a nearly constant refractive index for the glass slab across various
angles of incidence.
Confirm that the emergent ray is parallel to the incident ray, albeit laterally displaced, a characteristic behavior
for light passing through parallel-sided media.
Observe that the lateral displacement increases with the angle of incidence, as expected theoretically.
The average refractive index of the glass slab was found to be approximately 1.516, which is consistent with the
known refractive index of glass. This experiment provided a practical understanding of fundamental optical
principles and reinforced skills in experimental design, precise measurement, and data analysis.
Limitations and Future Work
While the experiment yielded satisfactory results, limitations such as instrument precision and potential human
error were present. Future work could involve:
Using a laser light source for a more defined and precise ray path.
Employing a goniometer for more accurate angle measurements.
Investigating the effect of different colors of light (different wavelengths) on the refractive index and lateral
displacement (dispersion).
Bibliography/References
NCERT Physics Textbook for Class XII, Part 2. (Current Edition)
P.K. Mittal. Practical Physics. (Publisher, Year)
Serway, R. A., & Jewett, J. W. (2018). Physics for Scientists and Engineers with Modern Physics. Cengage
Learning.
https://byjus.com/physics/refraction-through-a-rectangular-glass-slab/
https://www.toppr.com/guides/physics-practicals/refraction-through-glass-slab/
Appendices
Original Tracing Sheets (if available, scanned or photographed)
Detailed Calculations for each trial of refractive index (sin i / sin r)
Photographs of the experimental setup during the procedure

21. Rpˆäacø•¾µ ¾ˆ L•‰ø •µ a Rpcøaµ‰Ā«aä G«aìì S«ab:
A PĞì•cì Iµėpìø•‰aø¾äĞ Pä¾¥pcø
This investigatory project explores the fundamental phenomenon of light refraction as it passes through a rectangular
glass slab. Through precise experimentation and data analysis, we aim to verify Snell's Law and deepen our understanding
of optical principles. This document outlines the structured approach taken, from theoretical foundations to experimental
procedures and conclusive findings, designed to meet the requirements for a Class 12 Physics practical examination.

22. Ac¨µ¾Ę«pj‰p³pµøì
This project would not have been possible without the invaluable support and guidance from several individuals. I extend
my sincere gratitude to:
My Physics teacher, [Teacher's Name], for their insightful guidance, constant encouragement, and for patiently clarifying
complex concepts throughout the project's duration. Their expertise was instrumental in shaping the experimental
design and data interpretation.
My parents, for their unwavering support, providing the necessary resources, and fostering an environment conducive to
learning and exploration. Their encouragement was a great source of motivation.
My peers, [Peer's Name 1] and [Peer's Name 2], for their constructive feedback during discussions and for sharing their
perspectives, which helped refine my understanding and approach.
The school laboratory staff, for ensuring the availability of all necessary equipment and for their assistance in setting up
the experimental apparatus.
Their collective contributions were vital to the successful completion of this project. Thank you.

23. Table of Contents
Title Page 1
Acknowledgements 2
Table of Contents 3
Abstract 4
Introduction 5
Theory 6
Experimental Setup 7
Observations and Results 8
Discussion 9
Conclusion 10
Bibliography/References 11
Appendices 12
This table provides a structured overview of the project, allowing for easy navigation through its various sections. Each
heading and subheading is listed with its corresponding page number for quick reference.

24. Abìøäacø
This project investigates the phenomenon of refraction of light as it passes through a rectangular glass slab. The primary
aim was to experimentally verify Snell's Law, which governs the relationship between the angles of incidence and refraction,
and to determine the refractive index of the glass material. Using a simple experimental setup involving a glass slab, a
protractor, and pins, angles of incidence, refraction, and emergence were measured for various incident angles.
The methodology involved tracing the path of light rays through the slab and accurately measuring the angles using
geometric principles. The collected data was then used to calculate the sine of these angles, and plots were generated to
illustrate the relationship predicted by Snell's Law. Preliminary findings indicate a consistent ratio of the sine of the angle of
incidence to the sine of the angle of refraction, confirming Snell's Law and yielding a refractive index value for the glass that
aligns with theoretical expectations for common glass types. This project provides a clear demonstration of optical
refraction and reinforces key physics concepts.

25. Iµøä¾jĀcø•¾µ
Light, a form of electromagnetic radiation, exhibits fascinating behaviors as it interacts with different media. One such
behavior is refraction, the bending of light as it passes from one transparent medium to another. This phenomenon is
fundamental to our understanding of optics and is responsible for a myriad of everyday occurrences, from the way lenses
focus light in cameras and eyeglasses to the shimmering appearance of objects submerged in water.
The study of refraction is critical in various scientific and technological applications, including the design of optical
instruments, fiber optics communication, and even the functioning of the human eye. Understanding how light bends at the
interface of two media is essential for predicting its path and manipulating it for practical purposes. This project
specifically focuses on the refraction of light through a rectangular glass slab, a simple yet powerful system for observing
and quantifying this phenomenon.
The objective of this investigatory project is threefold:
To observe and understand the path of light rays as they pass through a rectangular glass slab.
To experimentally verify Snell's Law of refraction.
To determine the refractive index of the glass material using experimental data.

26. Theory
Refraction is the change in direction of a wave passing from one medium to another or from a gradual change in the
medium. It is most commonly observed when a wave passes from one medium to another at an angle. In optics, refraction
refers to the bending of light as it travels from one transparent medium to another with a different optical density.
The underlying principle governing refraction is Snell's Law, which states that the ratio of the sine of the angle of incidence
(the angle between the incident ray and the normal to the surface) to the sine of the angle of refraction (the angle between
the refracted ray and the normal) is constant for a given pair of media. Mathematically, it is expressed as:
n sin» =1 1 n sin» 2 2
where:
is the refractive index of the first medium (e.g., air)n 1
is the angle of incidence» 1
is the refractive index of the second medium (e.g., glass)n 2
is the angle of refraction» 2
The refractive index ( ) is a dimensionless quantity that describes how fast light travels through the material. A higher
refractive index indicates a slower speed of light and a greater bending effect. Optical density is directly related to the
refractive index; a medium with a higher refractive index is considered optically denser. When light enters an optically
denser medium from a rarer medium, it bends towards the normal, and when it enters an optically rarer medium from a
denser medium, it bends away from the normal.
n

27. Experimental Setup
To conduct this experiment, the following materials were utilized:
Rectangular Glass Slab: A transparent block of glass with parallel faces, approximately 15 cm x 10 cm x 2 cm.
Drawing Board: A flat surface to secure the paper and glass slab.
White Paper Sheet: To trace the path of light rays.
Drawing Pins: To fix the white paper to the drawing board.
Optical Pins: Four or more sharp pins to mark the path of light rays.
Protractor: For measuring angles accurately.
Pencil: For drawing lines and marking points.
Ruler: For drawing straight lines and measuring lengths.
Procedure:
Secure a white sheet of paper onto the drawing board using drawing pins.1.
Place the rectangular glass slab in the middle of the paper and trace its outline with a pencil. Label the corners A, B, C,
D.
2.
Remove the glass slab. Draw a normal (a perpendicular line) to the surface AB at point O, approximately in the center.3.
Draw a line PO representing the incident ray, making an angle of incidence ( ) with the normal. Choose angles such as
30°, 40°, 45°, 50°, and 60° for variation.
4. »
1
Place the glass slab back precisely on its outline.5.
Fix two optical pins, P1 and P2, vertically on the incident ray PO, at a reasonable distance from each other.6.
Looking from the opposite side of the glass slab (face CD), fix two more optical pins, P3 and P4, such that P3 and P4
appear to be in a straight line with the images of P1 and P2 seen through the slab.
7.
Remove the glass slab and the pins. Draw a line through P3 and P4 to meet the surface CD at point O'. This line
represents the emergent ray.
8.
Join O and O'. This line represents the refracted ray inside the glass slab.9.
Draw a normal to the surface CD at point O'.10.
Measure the angle of incidence ( ), the angle of refraction ( , the angle between OO' and the normal at O), and the
angle of emergence ( , the angle between the emergent ray and the normal at O') using the protractor.
11. » 1 » 2
» e
Record the measurements in a table.12.
Repeat the experiment for at least five different angles of incidence.13.

28. Observations and Results
The following data was collected during the experiment by measuring the angles of incidence, refraction, and emergence
for various incident angles. The values for and were then calculated to verify Snell's Law.sin» 1 sin» 2
1 30° 19.5° 0.500 0.334 1.50 30°
2 35° 22.5° 0.574 0.383 1.50 35°
3 40° 25.0° 0.643 0.423 1.52 40°
4 45° 28.0° 0.707 0.469 1.51 45°
5 50° 30.5° 0.766 0.508 1.51 50°
Graphical Analysis:
0
20
40
60
Angle of Incidence (»¡) sin »¡ sin »¢
A graph plotting versus would yield a straight line passing through the origin, with its slope representing the
refractive index of the glass slab. The constant ratio of across different readings supports Snell's Law.
sin» 1 sin» 2
sin» / sin» 1 2

29. D•ìcĀì앾µ
The experimental results presented in the previous section largely support the theoretical principles of refraction and
provide a strong verification of Snell's Law. As observed from the data, the ratio of remained remarkably
consistent, yielding an average refractive index of approximately 1.51. This value is well within the expected range for
typical glass, such as crown glass (n j 1.52) or flint glass (n j 1.6 to 1.7), further affirming the accuracy of the experiment.
sin»
/ sin»
1 2
Furthermore, the observation that the angle of emergence ( ) was consistently equal to the angle of incidence ( ) is a
crucial finding. This confirms that for a rectangular glass slab, the emergent ray is parallel to the incident ray, indicating that
there is no net deviation of the light ray as it passes through the parallel faces. However, a lateral shift occurs, which could
be measured in more advanced experiments.
»e » 1
Despite the consistent results, several sources of potential error should be acknowledged:
Measurement Error: The accuracy of angle measurements using a protractor is limited, leading to slight variations in
readings. The thickness of the pencil lines and the width of the pins can also introduce minor inaccuracies.
Pin Alignment: Ensuring that the pins are perfectly vertical and that their images are in a perfectly straight line requires
careful observation and can be a source of human error.
Optical Density Variations: While assumed uniform, minor imperfections or variations in the density of the glass slab
could subtly affect the light's path.
Overall, the experiment successfully demonstrated the principles of refraction and provided a reliable method for
determining the refractive index of glass, aligning well with established physical laws.

30. C¾µc«Ā앾µ
This investigatory project successfully explored the phenomenon of light refraction through a rectangular glass slab.
Through meticulous observation and measurement, the project achieved its primary objectives:
The path of light rays as they traverse from air to glass and back to air was clearly observed and traced, demonstrating
the bending of light at the interfaces.
Snell's Law was experimentally verified, as the ratio of the sine of the angle of incidence to the sine of the angle of
refraction was found to be constant across various incident angles, within acceptable experimental error.
The refractive index of the glass slab was determined to be approximately 1.51, a value consistent with common types
of glass.
The experiment also reaffirmed that for a rectangular glass slab, the emergent ray is parallel to the incident ray, indicating
no angular deviation but a lateral displacement. This reinforces our understanding of light's behavior in parallel-sided
media.
Limitations and Future Work:
While the experiment provided valuable insights, certain limitations were noted, primarily related to the precision of manual
measurements. Future work could include:
Digital Measurement: Utilizing digital protractors or image analysis software for more accurate angle measurements.
Different Materials: Repeating the experiment with slabs made of different transparent materials (e.g., acrylic, water-
filled tanks) to compare their refractive indices.
Lateral Shift Measurement: Quantifying the lateral displacement of the emergent ray for various angles of incidence
and slab thicknesses.
Temperature Effects: Investigating how temperature changes might influence the refractive index of the glass.
This project serves as a foundational understanding of optical principles, paving the way for more complex explorations in
the field of optics.

31. To Study Refraction of Light in Rectangular Glass
Slab
This document outlines a comprehensive experimental study designed to investigate the phenomenon of light refraction
through a rectangular glass slab. Through detailed procedures, data collection, and rigorous analysis, we aim to understand
the fundamental principles governing how light bends as it passes from one medium to another. This study will reinforce
theoretical concepts with practical observation.

32. Introduction and Theoretical Background
Refraction is the bending of light as it passes from one transparent medium to another, caused by a change in its speed.
When light enters a denser medium (like glass from air), it slows down and bends towards the normal4an imaginary line
perpendicular to the surface at the point of incidence. Conversely, when it exits to a less dense medium, it speeds up and
bends away from the normal.
This behavior is governed by Snell's Law, which states: , where and are the refractive indices of the
first and second media, respectively, and and are the angles of incidence and refraction, measured with respect to the
normal. For a rectangular glass slab, light refracts twice: once upon entering the glass and again upon exiting. This results
in the emergent ray being parallel to the incident ray, but laterally displaced.
n sin» =1 1 n sin» 2 2 n 1 n 2
» 1 » 2

33. Objectives and Expected Outcomes
The primary objective of this experiment is to systematically observe and quantify the refraction of light through a
rectangular glass slab. Specifically, we aim to:
Verify Snell's Law by measuring angles of incidence and refraction.
Determine the refractive index of the glass material.
Investigate the lateral displacement of the emergent ray.
Analyze the relationship between the angle of incidence and the angle of emergence.
We expect to observe that as the angle of incidence increases, both the angle of refraction and the lateral displacement will
also increase. Furthermore, the angle of emergence should be equal to the angle of incidence, confirming the parallel
nature of the incident and emergent rays. The calculated refractive index should be consistent with known values for
common glass types (approximately 1.5).
1
Verify Snell's Law
Measure and compare angles to
validate the fundamental law of
refraction.
2
Determine Refractive Index
Calculate the optical density of
the glass slab material.
3
Quantify Lateral
Displacement
Measure the shift of the light ray
after passing through the slab.

34. Materials and Equipment Required
To conduct this experiment effectively, the following materials and equipment will be necessary. Precision in
measurements is crucial, so ensure all instruments are calibrated and in good working condition.
Optical Equipment
Rectangular glass slab (transparent, with polished
surfaces)
Light source (e.g., laser pointer or ray box)
Drawing board or cardboard sheet
White paper sheets
Protractor (for measuring angles)
Measurement and Support Tools
Sharp pencil
Drawing pins or pushpins
Ruler (for measuring lateral displacement)
Optical pins (at least 4)
Set squares or right-angle ruler (for drawing normals)

35. Experimental Setup and Procedure
Follow these steps carefully to set up the experiment and accurately trace the path of light through the glass slab.
01
Prepare the Setup
Fix a white paper sheet on the drawing board using drawing
pins. Place the rectangular glass slab centrally on the paper
and trace its outline with a pencil, labeling the vertices A, B,
C, D.
02
Draw Incident Ray and Normals
Draw a normal (N1O1) perpendicular to the surface AB at
point O1. Draw an incident line (PO1) at a chosen angle of
incidence ( ) to the normal N1O1.» 1
03
Place Optical Pins
Place two optical pins, P1 and P2, vertically on the line PO1
at a sufficient distance from each other.
04
Observe and Mark Emergent Ray
Looking from the opposite side of the glass slab (surface
CD), observe the images of pins P1 and P2. Place two more
optical pins, P3 and P4, such that they appear to be in a
straight line with the images of P1 and P2. Mark the
positions of P3 and P4.
05
Complete the Ray Diagram
Remove the glass slab and pins. Draw a line through P3 and
P4 (O2Q) representing the emergent ray. Join O1 and O2 to
represent the refracted ray within the glass. Draw a normal
(N2O2) perpendicular to surface CD at O2. Extend the
incident ray PO1 forward (dotted line P'O1) and draw a
perpendicular line from O2 to P'O1 to measure lateral
displacement.
06
Measure Angles and Displacement
Measure the angles of incidence ( ), refraction ( ), and
emergence ( ). Also, measure the lateral displacement (the
perpendicular distance between the extended incident ray
and the emergent ray). Repeat the experiment for at least 5
different angles of incidence.
» 1 » 2
» 3

36. Data Collection Methods and Tables
Accurate data collection is paramount for drawing valid conclusions. For each trial, precisely record the measured angles
and displacement in the table provided. Ensure the protractor is placed correctly, with its center coinciding with the point of
incidence and its baseline along the normal.
1
2
3
4
5
Additional notes for data collection:
Record readings to one decimal place for angles and two decimal places for displacement.
Perform multiple readings for each angle of incidence to minimize random errors and calculate an average.
Document any anomalies or observations made during the experiment that might affect the results.

37. Analysis of Light Refraction Patterns
Once data is collected, it's essential to visualize and interpret the patterns. Plotting the data will help in understanding the
relationships between the measured variables.
0
30
60
90
Angle of Incidence (°) Angle of Refraction (°) Angle of Emergence (°)
Plot a graph of Angle of Incidence vs. Angle of Refraction and another of Angle of Incidence vs. Lateral Displacement. This
will visually demonstrate Snell's Law and the relationship between the variables. Observe if the emergent ray is consistently
parallel to the incident ray, indicated by .» =1» 3
Visualizing the data helps identify trends and potential outliers more readily than numerical data alone.

38. Results and Discussion
Present the calculated average refractive index and discuss how well the experimental results align with theoretical
predictions and the objectives outlined earlier.
Key Findings
The average refractive index of the glass slab was
found to be approximately [Your Calculated Average].
The graph of Angle of Incidence vs. Angle of Refraction
demonstrated a clear non-linear relationship,
consistent with Snell's Law.
In nearly all trials, the angle of emergence was found to
be approximately equal to the angle of incidence,
confirming the parallel nature of the incident and
emergent rays.
Lateral displacement increased with the angle of
incidence, as theoretically expected.
Address any discrepancies between observed and expected results, linking them back to the error analysis. For example,
slight variations in the refractive index for different trials could be attributed to minor measurement inaccuracies. Discuss
the significance of the lateral displacement, noting its practical implications (e.g., how objects appear shifted when viewed
through thick glass).
Consider the role of wavelength: While not directly measured, discuss how refractive index is also dependent on
the wavelength of light, potentially leading to dispersion (though negligible for a single color light source).

39. Conclusion and Practical Applications
This experiment successfully demonstrated the principles of light refraction through a rectangular glass slab, verifying
Snell's Law and quantifying key optical phenomena. The emergent ray's parallelism to the incident ray, alongside its lateral
displacement, was clearly observed and measured, reinforcing our understanding of light's behavior at material interfaces.
Key Learnings:
Snell's Law Validated
The relationship between angles
of incidence and refraction was
consistent with theoretical
predictions, confirming the
fundamental law.
Lateral Shift Observed
The emergent ray was
parallel but displaced, a
direct consequence of
refraction through parallel
surfaces.
Refractive Index
Determined
Calculations provided an
approximate refractive index for
the glass, aligning with expected
values.
Practical Applications:
The principles studied are crucial in numerous fields:
Optics and Lenses: Understanding refraction is fundamental to designing lenses for eyeglasses, cameras, telescopes,
and microscopes.
Fiber Optics: Total internal reflection, a related phenomenon, is the basis for data transmission in fiber optic cables.
Medical Imaging: Techniques like endoscopy rely on light guidance through refractive principles.
Everyday Phenomena: Explains why objects appear distorted in water or through thick windows.
This study provides a solid foundation for further exploration into advanced optical concepts and their diverse applications
in technology and science.