will be useful !

1. INTRODUCTION
 White light is the combination of all of the colors of the visible spectrum of
light (which have different wavelengths). A prism is a clear, triangular
device made up of plastic or glass (or any transparent material). When
white light goes through a prism, the light bends due to the phenomenon
called refraction
 The visible spectrum. White light can be split up to form a spectrum using a
prism. This is a block of glass with a triangular cross-section. ... As a result,
red light is refracted the least and violet light is refracted the most, causing the
coloured light to spread out to form a spectrum.
 Refraction and the Rainbow. Refraction is a phenomenon that happens
when a beam of white light passes through the interface between air and a
denser medium, such as glass or water. ... Therefore, when the beam emerges
from the denser medium, it has been split into its component wavelengths
CAPSULE !
Do you know the Definition of pure spectrum? A spectrum
in which the dispersion is highly discriminative so that at each point the light is
practically monochromatic.

2. AIM
To investigate the types and function of ;
1. Prism
2. Spectrum

3. THEORY
 In optics, a prism is a transparent optical element with flat,
polished surfaces that refract light. At least two of the flat surfaces
must have an angle between them. 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.
 A dispersive prism can be used to break light up into its
constituent spectral colors (the colors of the rainbow).
Furthermore, prisms can be used to reflect light, or to split light
into components with different polarizations.
HOW PRISMS WORK ?
Light changes speed as it moves from one medium to another (for
example, from air into the glass of the prism). This speed change
causes the light to be refracted and to enter the new medium at a
different angle (Huygens principle). The degree of bending of the
light's path depends on the angle that the incident beam of light
makes with the surface, and on the ratio between the refractive

4. indices of the two media (Snell's law). The refractive index of
many materials (such as glass) varies with the wavelength or
color of the light used, a phenomenon known as dispersion. This
causes light of different colors to be refracted differently and to
leave the prism at different angles, creating an effect similar to a
rainbow. This can be used to separate a beam of white light into
its constituent spectrum of colors. A similar separation happens
with iridescent materials, such as a soap bubble. Prisms will
generally disperse light over a much larger frequency bandwidth
than diffraction gratings, making them useful for broad-spectrum
spectroscopy. Furthermore, prisms do not suffer from
complications arising from overlapping spectral orders, which all
gratings have.
Prisms are sometimes used for the internal reflection at the
surfaces rather than for dispersion. If light inside the prism hits
one of the surfaces at a sufficiently steep angle, total internal
reflection occurs and all of the light is reflected. This makes a
prism a useful substitute for a mirror in some situations.
TYPES OF PRISMS
Dispersive prisms
Dispersive prisms are used to break up light into its constituent spectral
colors because the refractive index depends on frequency; the white
light entering the prism is a mixture of different frequencies, each of
which gets bent slightly differently. Blue light is slowed down more
than red light and will therefore be bent more than red light.

5. 1) Triangular prism
2) Abbe prism
3) Pellin–Broca prism
4) Amici prism
5) Compound prism
6) Grism , a dispersive prism with a diffraction grating on its surface
Reflective prisms
Reflective prisms are used to reflect light, in order to flip, invert, rotate,
deviate or displace the light beam. They are typically used to erect the
image in binoculars or single-lens reflex cameras – without the prisms
the image would be upside down for the user. Many reflective prisms
use total internal reflection to achieve high reflectivity.
The most common reflective prisms are:
1) Porro prism
2) Porro–Abbe prism
3) Amici roof prism
4) Pentaprism and roof pentaprism
5) Abbe–Koenig prism
Beam-splitting prisms
Some reflective prisms are used for splitting a beam into two or more
beams:
1) Beam splitter cube
2) Dichroic prism

6. Polarizing prisms
There are also polarizing prisms which can split a beam of light into
components of varying polarization. These are typically made of a
birefringent crystalline material.
1) Nicol prism
2) Wollaston prism
3) Rochon prism
4) Sénarmont prism
5) Glan–Foucault prism
Deflecting prisms
 Wedge prisms are used to deflect a beam of light by a fixed angle.
A pair of such prisms can be used for beam steering; by rotating
the prisms the beam can be deflected into any desired angle
within a conical "field of regard". The most commonly found
implementation is a Risley prism pair. Two wedge prisms can also
be used as an anamorphic pair to change the shape of a beam.
This is used to make a round beam from the elliptical output of a
laser diode.
 Rhomboid prisms are used to laterally displace a beam of light
without inverting the image.
 Deck prisms were used on sailing ships to bring daylight below
deck, since candles and kerosene lamps are a fire hazard on
wooden ships.

7. SPECTRUM FORMATION
White light
 White light is a mixture of many different colours.
 White light can be split into a spectrum using a prism, a
triangular block of glass or perspex. Light is refracted (changes
direction) when it enters the prism, and each colour is refracted
by a different amount. Light leaving the prism is spread out into
its different colours, a process called dispersion.
 White light can be generated by a variety of sources both in
space and by artificial sources on Earth. For example, the Sun is
a source of white light. Artificial sources include fluorescent
light bulbs and white LEDs which produce white light. White
light is a mixture of many different colours, each with a
different frequency (number of waves that pass a point in space
in a time interval, usually one second ).
 White light can be split up into a spectrum of these colours
using a prism, a triangular block of glass or Perspex plastic.
Light is refracted when it enters the prism, and each colour is
refracted by a different amount. This means that the light
leaving the prism is spread out into its different colours, a
process called dispersion.

8.  When white light passes through a prism, it is dispersed and
the different colours of the spectrum separate. Dispersion
causes rainbows and the colours of the spectrum include: red,
orange, yellow, green, blue, indigo and violet (lowest to
highest frequency).
 Dispersion happens because the different colours of light travel
at different speeds in a medium such as glass. The amount of
bending increases as the change in speed increases, therefore
blue light bends more than red light.
Splitting white light
 White light can be split into a spectrum of many different
colours using a prism. This is a block of glass with a triangular
cross-section. The light waves are refracted as they enter and
leave the prism. The shorter the wavelength of the light the
more it is refracted. As a result, red light is refracted the least
and violet light is refracted the most, causing the coloured light
to spread out to form a spectrum.
 When a ray of light goes from one material to another, it bends.
The amount of bending depends on the angle at which it strikes
the surface, as well as on the difference in the speed of light in
the two materials. The bigger the speed difference, the more it
bends.
 Prisms work because the speed of light changes as it
moves from one medium to another (air to glass). The speed at
which it travels causes the light to be refracted and bend. All

9. light strikes the front of a prism at the same angle, but when it
hits the back of the prism, the different colours are travelling in
different directions due to the change in speed. The colours
strike the back of the prism at different angles. They come out of
the prism at different angles which separates then into the
colours of the spectrum. This creates an effect similar to a
rainbow
APPARATUS REQUIRED
 TRIANGULAR PRISM
 WHITE LIGHT
 DARK ROOM
 SHINY CARDBOARD OR NEAT WALL
PROCEDURE
TAKE THE PRISM, AND KEEP OVER THE TABLE.
ENSURE THAT THE ROOM CONSIDERED TO BE DARK FOR THE
LIGHT TO BE OBVIOUS.
PASS THE WHITE LIGHT THROUGH THE TRIANGULAR PRISM
GENTLY
OBSERVE THE LIGHT INSIDE THE PRISM CAREFULLY

10. NOTICE THAT THE LIGHT RAY DENSE AT TWO DIFFERENT
POINTS
ONE IN THE LIGHT ENTERING THE PRISM AND ANOTHER WHEN
IT LEAVES THE PRISM.
OBSERVATION
 WHEN THE LIGHT TRAVELS THROUGH THE PRISM, IT SPLIT
THE WHITE LIGHT INTO SEVEN DIFFERENT COLOURS.
 THOSE COLOURS ARE SHORTLY KNOWN AS { VIBGYOR }
 NAMELY:
VIOLET,INDIGO,BLUE,GREEN,YELLOW,ORANGE,RED.
 THEY APPEAR IN THE SAME ORDER, JUST LIKE A RAINBOW.
Conclusion
 PRISMS ARE MADE UP OF GLASS, THE SEVEN DIFFERENT
COLOURS COMING OUT OF THE PRISM CONSTITUTE SEVEN
DIFFERENT WAVELENGTHS.
 EACH COLOUR REPRESENTS DIFFERENT WAVELENGTHS OF THE
LIGHT
 THESE DIFFERENT WAVE LENGHTS TRAVELS AT DIFFERENT
SPACES AT THE GLASS

11.  THESE IS THE MAIN REASON FOR THE FORMATION OF THE
RAINBOW
 ANGLE OF REFRACTION IS DIFFERENT FOR THESE COLOURS AS
THEY HAVE DIFFERENT WAVELENGTHS
 WHEN LIGHT TOUCHES THE SURFACES OF THE PRISM,
REFRACTION TAKES PLACE AT THE BOUNDARY OF THE PRISM.
 IN EXAMPLE, BOUNDARY BETWEEN AIR AND THE GLASS
 THEN THE WHITE LIGHT SEPERATED INTO COMPONENTS
COLOURS SUCH AS
RED,ORANGE,YELLOW,GREEN,BLUE,INDIGO,VIOLET.
 REFRACTION IS THE CHANGE IN DIRECTION OF THE WAVE
DUE TO CHANGE IN ITS MEDIUM.
 WHEN THESE WAVELENGTHS REACHES THE OTHER SIDE OF
THE PRISM AT DIFFERENT ANGLES REFRACTION TAKES PLACE
AT THE SURFACE OF THE PRISM ( i.e; at the boundary of the glass
and the prism )
 THE ANGLE OF REFRACTION IS GREATER WHEN IT LEAVES THE
PRISM
 THIS SEPERATION OF VISIBLE LIGHT INTO ITS DIFFERENT
COLOURS IS KNOW AS DISPERSION. ALL THESE COLOURS
CONSTITUENT THE SPECTRUM
 THE ANGLE OF REFRACTION WHICH A LIGHT UNDERGOES
WHEN IT TRAVELS FROM ONE MEDIUM TO ANOTHER
MEDIUM IS DETERMINANT BY THE REFRACTIVE INDEX OF THE
GIVEN MEDIUM

12. PRECAUTION
"The two precautions that must be taken while preforming the
experiment of tracing the path of rays of light through a glass prism
are”
1) Make sure Glass of slab is clean and it must be free from air
bubbles.
2) Also, the Angle of incidence should be lies between 30 degree and
60 degree.