THICKNESS OF HAIR
Mentors: Dr. Sanjeeta Rani, Associate professor, Dept. of Physics
Dr. Amit Garg, Associate professor, Dept. of Electronics
Dr. Reena Sharma, Associate professor, Dept. of Electronics
Fellows: Mr. Sanjeev Kumar Pandey, Roll No.7065015, B.Sc. Physical
Science Part 3
Mr. Bharat Mishra, Roll No.7065006, B.Sc. Physical Science -3
THE STUDY THE THICKNESS OF HUMAN HAIRS AND
STABLISHMENT OF THE TREND OF HUMAN HAIR-THICNESS
WAS DONE BY STUDYING DIFFERACTION PATTERN
PRODUCED BY HAIRS, USING CCD (CHARGE COUPLING
DEVICE) AND DIGITAL STORAGE OSCILLOSCOPE THROUGH
NI LabVIEW SIGNAL EXPRESS TEKTRONIX
INTRDUCTION: Hairs are important sense organ of the human being,
particularly those on the eyelids and eyebrows, since they are involved in the
sin the sense of touch. Also hair carries an individual’s body odor, by which
he/she may be recognized. Human have much less visible hair than do other
primates like apes and monkeys. Surprisingly, however, a square cm of
human skin have greater number of hair producing sites, called follicles,
than the same area of the skin of other primates.
Biologically, hair is a filament, mostly protein, that grows from follicles
found in the dermis. The human body, apart from the palms of the hands and
soles of the feet, is covered in follicles which produce thick terminal and
fine vellus hair. Most common interest in hair is focused on hair growth, hair
types and hair care but hair is also an important biomaterial and the hair
follicle is a well studied biological organ.
Hair fibers are roughly cylindrical in structure, I’d thought of measuring the
thickness of the hairs using diffraction method and ‘Babinet principle’.
The formula that the principle suggests is:
nλ = (a+b) sinθ
Where, n-order of the diffraction
λ- Wavelength of the light used
(a+b)- Thickness of the slit/obstacle
θ- Angle between the light and the obstacle/slit
Apparatus and arrangements used: Hair mounters ( self made),laser
diode, laser diode mount, CCD, labVIEW software and associated
arrangements, DSO(Digital Storage Oscilloscope), grating slit mount,
rotation stage of optical bread board arrangement, screen , optical bench,
single slit, double slit, set of polarizer and analyzer.
Project Outline: (1) Preparation of samples: The samples of hair to be
tested were mounted on self prepared 2x1.5 inch card board slit. The samples
were fixed on the prepared slit by an appropriate adhesive while keeping the
hair straight and strained, so that diffraction pattern can be obtained
properly.
(2)Naming and grouping of the samples: The samples were named/
numbered and then they were divided according to their close age groups.
(3)Calibration of the setup: The calibration was done using double slit, and
necessary amendment/adjustment/changes/alteration was done.
(4)Actual sample measurement: actual samples were kept on the rotation
stage and the diffraction patterns were recorded using labVIEW
TEKTRONIX.
THEORY
LASER DIODE
A laser diode is a laser where the active medium is a semiconductor similar
to that found in a light-emitting diode. The most common and practical
type of laser diode is formed from a p-n junction and powered by injected
electric current. These devices are sometimes referred to as injection laser
diodes to distinguish them from (optically) pumped laser diodes, which are
more easily manufactured in the laboratory.
Theory of operation
A laser diode, like many other semiconductor devices, is formed by doping a
very thin layer on the surface of a crystal wafer. The crystal is doped to
produce an n-type region and a p-type region, one above the other, resulting
in a p-n junction, or diode.
Laser diodes form a subset of the larger classification of semiconductor p-n
junction diodes. As with any semiconductor p-n junction diode, forward
electrical bias causes the two species of charge carrier - holes and electrons to be "injected" from opposite sides of the p-n junction into the depletion
region, situated at its heart. Holes are injected from the p-doped, and
electrons from the n-doped, semiconductor. (A depletion region,devoid of
any charge carriers, forms automatically and unavoidably as a result of the
difference in chemical potential between n- and p-type semiconductors
wherever they are in physical contact.)
As charge injection is a distinguishing feature of diode lasers as compared to
all other lasers, diode lasers are traditionally and more formally called
"injection lasers.".When an electron and a hole are present in the same
region, they may recombine or "annihilate" with the result being
spontaneous emission — i.e., the electron may re-occupy the energy state of
the hole, emitting a photon with energy equal to the difference between the
electron and hole states involved. (In a conventional semiconductor junction
diode, the energy released from the recombination of electrons and holes is
carried away as phonons, i.e., lattice vibrations, rather than as photons.)
Spontaneous emission gives the laser diode below lasing threshold similar
properties to an LED.
The difference between the photon-emitting semiconductor laser (or
LED) and conventional phonon-emitting (non-light-emitting) semiconductor
junction diodes lies in the use of a different type of semiconductor, one
whose physical and atomic structure confers the possibility for photon
emission. The properties of silicon and SSSSSSthat do not align in the way
needed to allow photon emission .The transition between the materials in the
alternating pattern creates the critical "direct bandgap" property. Gallium
arsenide, indium phosphide, gallium antimonide, and gallium nitride are all
examples of compound semiconductor materials that can be used to create
junction diodes that emit light.