Transcript 1. AP Intro Optics GOOD

Introduction in Optics
Dipl.Ing.Nicoleta PRICOPI
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 Sources–LASER
The classical description of the light
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.
Wavelength ()
Frequency f=c/ 
Subunit
Symbol
m
centimeters
Cm
10-2
Subunit
Symbol
Hz
millimeters
Mm
10-3
kHz
103
micrometers
m
Kilohertz
10-6
Mmegahertz
MHz
106
nanometers
Nm
10-9
Ångstroms
Å
10-10
Gigahertz
GHz
109
picometers
Pm
10-12
Terahertz
THz
1012
femtometers
Fm
10-15
attommeters
Am
10-18
elecron-volt [1 eV ~ 2.41 x 1014 Hz]
• 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.
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:
E=h·f
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 J·s (Joule x Second)
= 4,14 x 10-15 eV.s (Electron volt x Second)
Bohr’s atom model
Niels Bohr postulated that: “the electrons in the atoms move in orbits about
their nuclei with only certain allowed energies”
Bohr defined the term energy level of an atom one of the allowed
energy values that an electron can have
Energy
E2
h
E1
The Colors and how we
see
 Rod cells
 Cones cells
The photoreceptors
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
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
Snell's Law:
N1 x sin(q1) = N2 x sin(q2)
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.
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.
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 sm
than the light’s wavelength and will spread out.
INTERFERENCE of the light
Interference is the interaction between waves traveling in the same medium.
Constructive
Interference
Destructive
Interference
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 dow
are called polarized light.
Basic Elements of Optical Systems
LENSES
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.

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.
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
LIGHT SOURCES
Light Amplification by Stimulated Emission of Radiation
LASER is a device that creates and amplifies a narrow, intense beam of coherent li
Absorption and Emission
Stimulated Emission
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.