Introduction in Optics

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Introduction in Optics
Dipl.Ing.Nicoleta PRICOPI
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Outline

• What is light?Relevant theories
• The Colors and how we see
• Reflection, Refraction, Dispersion, Diffraction
• Interference and Polarization of the light
• Elements of Optical Systems
• Light SourcesLASER

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The classical description of the light
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Wave properties

• Wavelength (?)
• Frequency (no. of oscillations/sec)
• Amplitude (the height of the wave)the square
• of the amplitude intensity of the wave
• Energy
• Velocity c 3 x 108 m/s.

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Wavelength (?)
Frequency fc/ ?
Subunit Symbol m
centimeters Cm 10-2
millimeters Mm 10-3
micrometers ?m 10-6
nanometers Nm 10-9
Ångstroms Å 10-10
picometers Pm 10-12
femtometers Fm 10-15
attommeters Am 10-18
Subunit Symbol Hz
Kilohertz kHz 103
Mmegahertz MHz 106
Gigahertz GHz 109
Terahertz THz 1012
elecron-volt 1 eV 2.41 x 1014 Hz
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• I part (optical spectrum) includes the spectrum
  of visible light, IR spectrum and UV
• spectrum
• the IInd part comprises microwaves spectrum,
  radio-frequencies spectrum and power
• frequences spectrum
• the IIIrd part contains X-rays spectrum and
  gamma-rays spectrum.

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The quantum mechanical description of the light

• Light particles called photons (quanta of
  electromagnetic energy).
• In 1900 Max Planck introduced of the idea of
  quantization of energy postulating that the
  energy of any oscillator can not be any desired
  value, but only the value related to its
  frequency.
• Planck described light as discrete bundles of
  energy and proposed that the energy of a single
  photon is
• Ehf
• where
• f is the frequency of the light
• n is the index of refraction of the medium (n
  1 for open space)
• h is the Planck constant, which has the value
• h 6.62 x 10-34 Js (Joule x Second)
• 4,14 x 10-15 eV.s (Electron volt x Second)

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Bohrs atom model

• Niels Bohr postulated that the electrons in the
  atoms move in orbits about their nuclei with only
  certain allowed energies

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Bohr defined the term energy level of an atom one
of the allowed energy values that an electron
can have
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The Colors and how we see
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• Rod cells
• Cones cells

The photoreceptors
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REFLECTION of the light

• The reflection of light can be roughly
  categorized into two types of reflection
• specular reflection defined as light reflected
  from a smooth surface at a definite angle
• diffuse reflection, which is produced by rough
  surfaces that tend to reflect light in all
• directions

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REFRACTION of the light
Refraction (or bending of the light) occurs as
light passes from a one medium to another when
there is a difference in the index of refraction
between the two materials. Refractive index (N)
is defined as the relative speed at which light
moves through a material with respect to its
speed in a vacuum. The index of refraction, N,
of other transparent materials is defined through
the equation
By definition, the refractive index of a vacuum
is defined as having a value of 1.0
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When N(1) is greater than N(2), the angle of
refraction is always smaller than the angle of
incidence. Alternatively when N(2) is greater
than N(1) the angle of refraction is always
greater than the angle of incidence. When the
two refractive indices are equal (N(1) N(2)),
then the light is passed through without
refraction.
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dispersion of the light
The index of refraction varies with the frequency
of radiation (or wavelength) of light. This is
occurs with all transparent media and has been
termed dispersion. As the wavelength of light
increases, the refractive index decreases. It is
the dispersion of light by glass that is
responsible for the familiar splitting of light
into its component colors by a prism.
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diffraction of the light
Diffraction is the process by which light waves
traveling throught a small hole or slit that is
phzsically the approximate size of even
smaller than the lights wavelength and will
spread out.
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INTERFERENCE of the light
Interference is the interaction between waves
traveling in the same medium.
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Constructive Interference
Destructive Interference
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polarization of the light
Light waves can vibrate in many directions.
Those that are vibrating in one direction in a
single plane such as up and down are called
polarized light.
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Basic Elements of Optical Systems
LENSES
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Single Lens Conventions

• The object is placed to the left of the lens.
• Real images fall to the right of the lens.
• Virtual images fall to the left of the lens.
• The object distance do, is always positive.
• The image distance di, is positive for real
  images and negative for virtual images.
• The focal length, f, is positive for a
  converging lens and negative for a diverging
  lens.
• The magnification, m , is positive for an
  upright image and negative for an inverted image.

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Reflection of Light-Mirrors
The image in a plane mirror is upright,
left-right reversal, same size, and located as
far behind the mirror and the object is in front
of the mirror.
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Spherical Mirrors
Concave Mirror Images

• Radius of Curvature (R)
• Center of Curvature (C)
• Focal point (F)
• Focal length (f)
• f 1/2R

Convex Mirror Images
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LIGHT SOURCES
Light Amplification by Stimulated Emission of
Radiation
A LASER is a device that creates and amplifies a
narrow, intense beam of coherent light.
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Absorption and Emission
Stimulated Emission
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Population Inversion
Characteristics of Laser Light
1.Coherence. Different parts of the laser beam
are related to each other in phase. 2.
Monochromaticity. Laser light consists of
essentially one wavelength, having its origin in
stimulated emission from one set of atomic energy
levels. 3.Collimated-laser beams are very narrow
and do not spread very much.
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