Refraction Through Prism & Finding Angle of Deviation Experiment for i = 45 | Physics Demo STD 10
Summary
TLDRThis video tutorial focuses on the practical aspects of using a glass prism in an experiment, addressing common queries and misconceptions. It explains that the angle of incidence is not equal to the angle of emergence in a prism, except in the special case of minimum deviation. The step-by-step demonstration includes setting up the experiment, measuring angles, and determining the angle of deviation. The tutorial emphasizes accuracy and allows for minor human errors, encouraging viewers to comment with any doubts. The video concludes with a thank you message for the support received.
Takeaways
- 🔬 The experiment involves using a glass prism to demonstrate the principles of light refraction and the angles involved, clarifying that the angle of incidence is not equal to the angle of emergence in a prism, unlike a glass slab.
- 📚 The script emphasizes the special case of 'minimum deviation' where the angles of incidence and emergence are equal, which only occurs when the prism is positioned in a specific way.
- 📏 The experiment requires marking and measuring angles accurately, using a protractor to determine the angle of incidence, which is set at 45 degrees in this demonstration.
- 📍 The setup includes an A4 size paper attached to a wooden board, with pins used to align and mark the paths of light rays.
- 📌 The experiment involves aligning pins to create a straight line with the images of the pins seen through the prism, ensuring the accuracy of the light path observation.
- 👀 It's important to view the experiment from the correct angle, with one eye closed and the eye parallel to the surface of the prism to observe the alignment of the pins' images.
- 📝 The script instructs on marking the locations where the pins are aligned with the images, which helps in tracing the path of the light rays.
- 📐 The angle of emergence is measured using a protractor, and it is found to be approximately 53 degrees in this experiment, differing from the angle of incidence.
- 📉 The angle of deviation is calculated by extending the incident and emergent rays and measuring the angle between them, which is approximately 38 degrees.
- 🔍 The refractive index can be determined using Snell's law and the measured angles of incidence and emergence.
- 📊 The experiment concludes with the suggestion to plot a graph of the angle of incidence versus the angle of deviation to find the minimum deviation and understand the relationship between these angles.
Q & A
What is the main purpose of repeating the prism experiment in the video?
-The main purpose is to clarify the misconception that the angle of incidence is always equal to the angle of emergence when dealing with a glass prism, and to demonstrate the correct procedure for conducting the experiment.
Why is the angle of incidence not equal to the angle of emergence in a glass prism experiment?
-The angle of incidence is not equal to the angle of emergence in a glass prism experiment because it only happens in a special case known as the minimum deviation case. This does not occur with a glass slab where the angles are generally equal.
What special case allows the angle of incidence to be equal to the angle of emergence in a prism?
-The special case is known as the minimum deviation case. When the prism is positioned to achieve minimum deviation, the angle of incidence becomes equal to the angle of emergence.
How is the angle of incidence set in the experiment described in the script?
-The angle of incidence is set by using a protractor to mark a 45-degree angle on the A4 size paper where the prism is placed.
What is the significance of marking the center of the A4 size paper with a dot?
-Marking the center of the A4 size paper with a dot helps to accurately place the prism and ensures that the experiment is conducted symmetrically around the center point.
Why are two pins used in the experiment, and what is their purpose?
-Two pins are used to create a reference for the angle of deviation. They are placed at a distance and their images are aligned to form a straight line, which helps in determining the path of the refracted and emergent rays.
What is the approximate distance between the two pins used in the experiment?
-The approximate distance between the two pins is about 7 centimeters, as mentioned in the script.
How is the angle of emergence measured in the experiment?
-The angle of emergence is measured by aligning a protractor with the emergent ray and the normal to the prism surface, then reading the angle formed.
What is the method to find the angle of deviation in the experiment?
-The angle of deviation is found by extending the emergent and incident rays with dotted lines and measuring the angle formed between the extended lines using a protractor.
How can the refractive index be determined using the angles of incidence and emergence?
-The refractive index can be determined using Snell's law, which relates the angle of incidence and the angle of refraction. By measuring these angles, one can calculate the refractive index of the prism material.
What is the significance of plotting a graph of the angle of incidence versus the angle of deviation?
-Plotting a graph of the angle of incidence versus the angle of deviation helps to visualize the relationship between these angles and to identify the minimum deviation point, which is important for understanding the optical properties of the prism.
Outlines
🔬 Prism Experiment Revisited
The speaker reiterates the importance of understanding the behavior of light through a glass prism, clarifying misconceptions about the equality of angles of incidence and emergence. They emphasize that this only holds true in the special case of minimum deviation. The practical demonstration involves setting up an experiment with a protractor and pins on an A4 paper to measure the angle of incidence at 45 degrees. The goal is to align the images of the pins with the prism to appear in a straight line, illustrating the path of light through the prism.
📏 Measuring Angles in the Prism Experiment
After setting up the experiment, the speaker proceeds to measure the angle of emergence and deviation using a protractor. They carefully mark the locations where the pins were placed, join these points to the prism surface, and measure the angles formed. The speaker explains the process of finding the angle of deviation by extending the rays and measuring the angle formed between the extended emergent and incident rays. They also mention the possibility of slight human error in the experiment and how it can affect the results.
📈 Analyzing and Plotting Prism Experiment Data
The speaker concludes the experiment by discussing the analysis of the measured angles and the importance of plotting a graph of angle of incidence versus angle of deviation. They mention the concept of minimum deviation and how the angle of incidence equals the angle of immersion at this point. The speaker encourages viewers to perform the experiment with different angles of incidence to understand the relationship between the angles more clearly. They also address common concerns about the equality of certain angles in the experiment and emphasize the acceptability of minor discrepancies.
Mindmap
Keywords
💡Prism
💡Angle of Incidence
💡Angle of Emergence
💡Minimum Deviation
💡Refraction
💡Snell's Law
💡Refractive Index
💡Angle of Deviation
💡Equilateral Triangle
💡Practical Experiment
💡Graph Plotting
Highlights
The angle of incidence is not equal to the angle of emergence in a glass prism, unlike in a glass slab.
Angle of incidence equals angle of emergence only in the special case of minimum deviation in a prism.
In the experiment, a glass prism is placed on an A4 size paper, and a protractor is used to measure angles.
The angle of incidence is set to 45 degrees, and pins are used to trace the light path.
Two pins are placed at a distance of at least 5 centimeters from each other to determine the path of the incident ray.
The emergent ray is traced by aligning two additional pins with the images of the first two pins as seen through the prism.
The angle of emergence is measured using a protractor and found to be roughly 53 degrees.
The angle of deviation is determined by extending the emergent ray backward and the incident ray forward.
The angle of deviation is measured to be approximately 38 degrees.
The angle of refraction is found to be around 33 degrees using the refracted ray.
The sum of the angle of incidence and the angle of emergence should be equal to the sum of the angle of the prism and the angle of deviation, allowing for minor human error.
For a 60-degree prism, the calculation shows that 45 degrees (incidence) + 53 degrees (emergence) equals 98 degrees, and 60 degrees (prism) + 38 degrees (deviation) also equals 98 degrees.
The experiment allows for an error margin of about one or two degrees.
To obtain the minimum deviation graphically, different angles of incidence are tested, and a graph is plotted with the angle of incidence on one axis and the angle of deviation on the other.
The point of minimum deviation on the graph indicates where the angle of incidence equals the angle of emergence.
Transcripts
and I am going to repeat the Bold
practical of prism once again
there are many queries in that
particular experiment so I have decided
to make video once again please note
that
this is a glass prism that we are going
to use and unlike the glass slab
angle of incidence will not be equal to
the angle of emergence it happens only
in the glass slab many many people have
commented that I should be equal to e
But please understand that angle of
incidence is equal to angle of emergence
in all cases in case of glass lab not in
case of prism it happens only in a
special case which is known as minimum
deviation case so when the prism is in
minimum deviation at that time only the
angle of incidence and emergence are
equal so practically we don't know which
angle
V for the angle of incidence we will get
the minimum deviation right
so please do not expect that angle of
incidence will be equal to angle of
emergence in case of the class prism
right
so now let's quickly proceed further and
I'm going to make the angle of incidence
45 degree this time and I am going to
repeat the practical
so as you can see that I have uh
clamped two soft board pins on an A4
size paper these are some basic
stationeries and this A4 size paper is
well attached on this wooden board
so now we are going to take the prism
and we are going to place it exactly at
the center of the A4 size paper we are
going to press it with our thumb and we
are going to out mark it
[Music]
like this
okay
now exactly at the center I am going to
make a DOT
then I am going to place the protractor
and
one dot I am going to make it at 90
degree
another at 45 degree
this line
is the normal
which is perpendicular to the surface
now this is going to be my incident rate
this is 90 degree this is 45 degree so
the angle of incidence is 45 degree
now
we are going to place
two pins
which are at least at a distance of
5 Centimeters from each other
please note that when you fix the pins
you will find it
the pins to be not piercing at some
locations
so you try different areas do not take
up the prism and try to bang it right
that looks very very odd so now
approximately I would think that the
distance is more than yes it is more
than 5 Centimeters this is roughly
six point six centimeters no it's all
approximately seven centimeters okay so
we are good to go now I am going to
place the prism back at the traced
location and then I'm going to see the
images of these two pins from this side
and then I am going to place another two
pins
here such that one here and the another
here such that these two pins and the
images of these two pins appear in a
perfect straight line
you need to get down from where you are
sitting
and you need to close one of your eyes
your eyes must be parallel
to the surface of the bone
as you can check by yourself that the
images of those two blue pins they are
appearing from this side of the prism
[Music]
[Music]
foreign
[Music]
pins they are appearing in the perfect
straight line This step has to go very
very well for the accuracy of the
experiment
now I am going to remove the pins
and mark the pricked locations
I am going to place the prism back at a
safe place remove these two pins and now
I am going to join these two points with
this prism surface let me name the prism
surface is as ABC then I am going to
join these two points P1 and P2 which
are the brick locations with the surface
AC of the prism
this is going to be my emergent Ray
now I am going to join these two points
this is say Point P3 and this is point
P4
this is going to be my refracted Ray
refracted Ray this is incident Ray
this is refracted Ray this one is the
emergent Ray now very carefully I am
going to place the protractor back
at surface AAC
and this point should be matching with
this point
like this
line of the protractor should match with
surface AC
now pointing at
90 degree
this is my normal
I'm going to join these two points let
the normal be long enough
[Music]
so this is my angle of emergence e and I
am going to measure the angle of
emergence by using the protractor please
put the protractor like this such that
this line should match with our emergent
Ray
like this one and this point of the
protractor must match with the
this particular point so I'm getting the
angle of emergence
as
this is 10 20 30 40 50 roughly around 53
degrees so this is the angle of
emergence which is 53 degrees now how
would we find out the angle of deviation
you need to extend this emergent Ray
backwards with a dotted line
like this
and extend the incident Ray forward
like this then the angle which is formed
this angle is the angle of deviation so
we are going to put the protractor back
at its place like this
and then we are going to measure the
angle of deviation
yeah
so from here to here this is 10 degree
20 degree 30 degree and this is
somewhere around 38 degrees so the angle
of deviation is roughly 38 degrees and
please understand that I and E are not
equal now I am just going to write down
all the angles over here this would be
our angle of refraction let us measure
that too
[Music]
for that I will have to extend this
refracted Ray forward
like this one and
then
10 20 30 roughly around 33 degrees is
the angle of refraction
you can also verify with the help of the
Snell's law so angle of
incidence is 45 degree you can also find
out the refractive index using these two
values
the angle of emergence and deviation are
as follows
sorry this is 38 degree and this is 53
degrees
now
I plus e
should be equal to a plus Delta but
since we are doing the experiment there
can be a human error of about one or two
degrees that's perfectly fine you need
not to exactly make them equal okay so I
is 45 degree plus e so that is 45 plus
53 this answer turns to be around
98 Degrees whereas a plus Delta a plus
Delta is equal to the angle of prism is
60 degrees because it is an equilateral
triangle
so 60 degrees plus 38 degrees so this is
perfectly 98 Degrees I was not expecting
this one but if you really do it with a
great trigger you may get the correct
answer if these two are not equal that's
perfectly fine many people have
commented a lot about this that these
two angles are not equal but that's
perfectly fine
two degrees error here and there is
allowed in the experiment you need not
to worry about that so now
all the angles are given and similarly
you can make the angle of incidence as
60 degrees 30 degrees other angles and
then you can find out the other angles
as well finally you will need to plot a
graph of
I
and Delta so here the angle of deviation
and then here the angle of incidence and
then for all the other values you will
have to plot the graph for angle of
incidence and for the angle of deviation
you will get similar kind of graph
this is the point which is the minimum
deviation Delta minimum and over here at
that angle the angle of incidence will
be equal to the angle of immersion so
you have to obtain that part graphically
so I hope this practical is now very
much clear to you still if you have any
doubts please do comment in the comment
section and I am really really very very
thankful to all of you that your support
has made my channel a very very big
success so once again pranam and
namaskar to everybody thank you very
much thanks a lot
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