TOPIC-PRISM

NAME:YEDUVAKA LELA MOHAN

CLASS:XII SEC:SCIENCE(A)
ROLL NUMBER:
BATCH:2019-2020
CERTIFICATE
 acknowledgement

Primarily I Would Thank GOD For Being Able To Complete

This Project With Success. Then I Would Like To Thank My

Physics Teacher MRS.JYOSTHA MAM

ValuableGuidance Has Been The Ones That Helped

Me Patch This Project And Make It Full Proof

Success Her Suggestions And Instructions

Has Served As The Major Contributor

Towards The Completion Of The Project.

Then I Would Like To Thank My PARENTS AND

FRIENDS Who Have Helped Me With Their Valuable

Suggestions And Guidance Has Been Helpful In Various

Phases Of The Completion Of The Project.

.
 CONTENTS
1.WHAT IS A PRISM
2.HOW DO PRISM WORK
3.TYPES OF PRISM
4.HALLOW PRISM
5.TOTALLY REFLECTING PRISM
6.THEORY OF LIGHT AND REFRACTION
7.HISTORY OF PRISM
8.APPLICATIONS OF PRISM

9.BIBLIOGRAPHY

WHAT IS A PRISM...?
Prism, in optics, piece of glass or other transparent
material cut with precise angles and plane faces,
useful for analyzing and reflecting light. An ordinary
triangular prism can separate white light into
its constituent colours, called a spectrum.
Each colour, or wavelength, making up the white
light is bent, or refracted, a different amount; the
shorter wavelengths (those toward the violet end of
the spectrum) are bent the most, and the longer
wavelengths (those toward the red end of the
spectrum) are bent the least. Prisms of this kind are
used in certain spectroscopes, instruments for
analyzing light and for determining the identity and
structure of materials that emit or absorb light.

HOW DO PRISMS WORK...?

In the 1600s, Isaac Newton did a series of
experiments with prisms and light. He showed that
prisms not only split light into the familiar rainbow
colors, but can also recombine them. The glass of a
prism, and the angles of its sides, work together to
make a fascinating optical tool.
Effects of Light:
When light passes from the air into glass, it slows
down, and when it leaves the glass, it speeds up
again. If the light hits the glass at an angle instead
of dead-on, it undergoes refraction. The angle at
which it hits the glass is not the same as the angle it
travels inside the glass. The light is no longer
moving in a straight line, but gets bent at the
surface. The same thing happens when the light
leaves the prism--it bends again.
Snell's Law:
An optical principle called Snell’s Law predicts
exactly how this happens. Snell’s Law deals with the
angles that light enters and leaves a prism, and
something called the index of refraction. The index
of refraction shows how much light slows down
when it goes into the glass.

Color Changes:
The different colors of light, from red to violet, each
get bent at slightly different angles. Red gets bent
the least, violet the most. This causes the colors to
fan out and become distinct.

Second Prism:
The fact that a prism can break light into colors was
known before Newton. But Newton asked what
would happen if he put a second prism in the
location of the colors. If the second prism caught all
the colors on one of its surfaces, white light came
out of the other side. The same properties that
spread the colors apart worked in reverse to
reassemble them.
Additional Experiments:
Newton also asked what would happen if he used a
second prism on only one color. Would it break into
other colors? His experiment showed that it didn’t.
The colors coming out of a prism are fundamental.
Reflection:
In addition to refracting light, prisms are also good
for reflecting light. If you look into a prism and turn
it in your fingers, you’ll see light reflected off the
back side at certain angles. This is called internal
reflection. Some prisms are designed to have several
internal reflecting faces. They can take a telescope
image that is upside-down and backwards and flip it
back to normal. Reflecting prisms are used in
periscopes and binoculars, as they are more durable
than mirrors.
TYPES OF PRISMS:
 Dispersive Prisms: they are used to break up
light into its constituent spectral colours. The
refractive index depends on the frequency. The
white light that enters the prism has a mixture of
different frequencies, and each frequency bends
differently. Eg. Abbe prism, Amici prism,
Compound prism
 Reflective Prisms: these are used for reflecting
light, for flipping, inverting, rotating, or displacing
the light beam. They are generally used for
erecting the image in binoculars or single-lens
reflex cameras. Without the use of prisms, the
image would become upside down for the very
user. Reflective prisms often use total internal
reflection for achieving higher reflectivity. Eg.
Porro prism, Pentaprism, Dove prism
Polarizing Prisms: they can split a beam of light
into the components of varying polarization. They
are generally made up of birefringent crystalline
material. Eg. Nicol prism, Rochon prism, Wollaston
prism
 Deflecting prims: Wedge prisms are used for
deflecting a beam of light by a fixed angle. A
 handful of such prisms are used for beam
steering. Rhomboid prisms laterally displace a
beam of light without the inversion of image.
Deck prisms bring daylight below the deck on the
sailing ships.

DISPERSIVE PRISM REFLECTIVE PRISM

DEFLECTING PRISM POLARIZING PRISM

WHAT IS A HALLOW PRISM ?

A hollow prism is a prism made using glass plate with the
center part of the prism is vacant. This cavity can be filled with
gas or other fluids. Thus, a hollow prism is also commonly
called as a fluid prism.
Why is there no dispersion in
hollow prism?

When white light passes through the prism ,different colours

suffers deviation through different angles and light appears to
be dispersed. But in a hollow prism dispersion does not take
place as all the colours travel with same speed in the air
inside hollow prism. Thus no angular dispersion is there.

What happens when light passes

through a hollow prism?

When a white light passes through the hollow prism, it

escapes out as it entered because no refraction takes place.
No, When beam of light passes through a prism, there is no
spectrum. Actually, Spectrum is produced by the deviation of
different colors due to the refraction of light.

what is a totally
reflecting prism?
A Right angled isosceles prism,i.e.,a 45°-90°-45° prism.Whenever a ray
falls normally on any face of such a prism,it is incident on the inside face
at 45°,that is at an angle greater than the critical angle of glass(42°); hence
this ray is always totally internally reflected.

THESE PRISMS MAY BE USED IN THREE WAYS:

(i)TO DEVIATE A RAY THROUGH 90°

(ii)TO DEVIATE A RAY THROUGH 180°

(iii)INVERT AN IMAGE WITHOUT THE DEVIATION OF RAYS

ADVANTAGES OF TOTALLY REFLEFTING PRISMS OVER PLANE MIRROR:

1.IN PRISMS ,THE LIGHT IS TOTALLY REFLECTED,WHILE THERE IS ALWAYS

SOME LOSS OF INTENSITY IN CASE OF PLANE MIRRORS.

2.TH REFLECTING PROPERTIES OF PRISMS ARE PERMANENT,WHILE THESE

ARE AFFECTED BY TARNISHING IN CASE OF PLANE MIRRORS.

3.NO MULTIPLE IMAGES ARE FORMED IN PRISMS,WHILE A PLANE

MIRROR FORMS A NUMBER OF FAINT IMAGES IN ADDITIONAL TO A
PROMINENT IMAGE.

THEORY: LIGHT AND REFRACTION

Understanding how a prism works is key to deciding which type of prism
fits best for a specific application. In order to do so, it is important to first
understand how light interacts with an optical surface. This interaction is
described by Snell's Law of Refraction:

(1)n1sin(θ1)=n2sin(θ2)n1sin(θ1)=n2sin(θ2)

Where n1 is the index of the incident medium, θ1 is the angle of the

incident ray, n2 is the index of the refracted/reflected medium, and θ2 is
the angle of the refracted/reflected ray. Snell's Law describes the
relationship between the angles of incidence and transmission when a ray
travels between multiple media (Figure 3).

Figure 3: Snell's Law and Total Internal Reflection

A prism is notable for its ability to reflect the ray path without the need for
a special coating, such as that required when using a mirror. This is
achieved through a phenomenon known as total internal reflection (TIR).
TIR occurs when the incident angle (angle of the incident ray measured
from normal) is higher than the critical angle θc:

(2)sin(θc)=n1n2sin(θc)=n1n2
Where n1 is the index of refraction for the medium where the ray
originates, and n2 is the index of refraction for the medium where the ray
exits. It is important to note that TIR only occurs when light travels from a
high index medium to a low index medium.

At the critical angle, the angle of refraction is equal to 90°. Referencing

Figure 3, notice that TIR occurs only if θ exceeds the critical angle. If the
angle is below the critical angle, then transmission will occur along with
reflection as given by Snell's Law. If a prism face does not meet TIR
specifications for the desired angle(s), then a reflective coating must be
used. This is why some applications require coated versions of a prism
that would otherwise work well uncoated in another application.

History of prisms...

René Descartes had seen light separated into the colors of the
rainbow by glass or water,[1] though the source of the color was
unknown. Isaac Newton's 1666 experiment of bending white light
through a prism demonstrated that all the colors already existed in
the light, with different color "corpuscles" fanning out and traveling
with different speeds through the prism. It was only later
that Young and Fresnel combined Newton's particle theory
with Huygens' wave theory to explain how color arises from the
spectrum of light.

Newton arrived at his conclusion by passing the red color from one
prism through a second prism and found the color unchanged. From
this, he concluded that the colors must already be present in the
incoming light — thus, the prism did not create colors, but merely
separated colors that are already there. He also used a lens and a
second prism to recompose the spectrum back into white light. This
experiment has become a classic example of the methodology
introduced during the scientific revolution.
The results of the experiment dramatically transformed the field
of metaphysics, leading to John Locke's primary vs secondary quality
distinction.[citation needed]

Newton discussed prism dispersion in great detail in his

book Opticks.[2] He also introduced the use of more than one prism to
control dispersion.[3] Newton's description of his experiments on prism
dispersion was qualitative. A quantitative description of multiple-
prism dispersion was not needed until multiple prism laser beam
expanders were introduced in the 1980s.[4]

APPLICATIONS OF PRISMS


 Prisms are often used in ophthalmology to help in diagnosing and

treating a number of eye diseases like esotropia, nystagmus,
amblyopia, exotropia etc. Opthalmologists use the light reflected and
refracted from prisms for examining different parts of the eye for
problems. Prisms also come in handy for redirecting the light
entering the eye for enhancing eye vision.
 Prisms are often used in optical instruments like binoculars, cameras,
telescopes, periscopes of submarines, microscopes etc as prisms have
the ability to bend and manipulate light.
 Prisms as a shape occur commonly in architecture. Eg on prism
shaped house roof tops, snow runs off the slopes rather than
accumulation.
 Prism helps in understanding the properties of light.
 BIBLIOGRAPHY

 NCERT TEXT BOOK

 S.L.ARORA PHYSICS
 WIKIPEDIA.COM
 JUSTSCIENCE.IN
 BRITANNICA.COM
 SCIENCING.COM