Waves, the Atom
and Optics
Carlos Silva
October 14th 2009
WAVES
Vibrations
Definition
Mechanical oscillation around an equilibrium point
• Mass-spring system oscillation
• Beam
• Drum
F  kx
Types of vibration
Free
• When we apply a force and then let the system vibrate with its natural frequency
Forced
• When we apply an alternated force (earthquake)
Systems vibrate due to the “Momentum Conservation” law
Period, Frequency and Amplitude
Period (s)
Interval of time measured in seconds that takes to repeat the vibration (T)
f 
Frequency (Hz=s-1)
Number of events/repetitions per second (f)
Wave length (m)
Distance between repeating units

V
f
Amplitude
Maximum variation during vibration (displacement, angle)
Vibrations are usually sinusoidal
This happens when the applied force is linear
This only happens for “small” amplitudes
This is called harmonic motion
1
T
Natural Frequency and Resonance
Natural frequency
fn 
Property of every system
k
m
Multiple modes of vibration (harmonics)
Multiples of the natural frequency
Resonance
Tendency to oscillate at maximum amplitude at natural
frequency
A force applied at the same frequency is providing
energy to the system at a rate that is higher than the
damping
Vibration modes
Damping
Damping
Mechanism of energy dissipation of vibration
Takoma bridge: www.youtube.com/watch?v=3mclp9QmCGs
Waves
Definition
Type of disturbance that propagates through time and space
Wave is a thing that transports energy and its not matter (doesn't obey Newton's laws)
They differ from matter in three ways:
• Superposition – two waves can be at the same place at the same time
• They transport energy, not the medium (the medium vibrates!)
• Wave velocity depends on the medium of propagation (does not depend on the
force – put energy into a wave “only” affects its amplitude)
Types of wave
Sound
Light
Water
Reflection, Transmission, Refraction and Absorption
Reflection
Change of a wave direction at an interface between two different media so that the
wave returns into the media where it was originated
Transmission
Wave changes the propagation mean
Refraction
Change of a wave velocity (and direction) when it changes media
Absorption
Change of the wave amplitude by the dissipation of its energy
Waves: Energy, wavelength, frequency
Light as matter, matter as wave
Wave-particle duality
concept that all matter and energy
exhibits both wave-like and
particle-like properties
• Corpuscles are light matter
• Nuclear particles that behaves like wave
THE ATOM
Atoms
Definition
Smallest unit of an element that retains its chemical
properties
Greek átomos that stands for indivisible
Nucleus
Protons (+)
Neutrons
Electrons cloud
Electrons(-)
Special orbits
They gain or loose energy while jumping from orbits
Bohr hydrogen (H) model
Number of protons= number of electrons
Oxygen (O) atom
Molecule
Molecule
Stable and electrical neutral combination of atoms
Water
90% of the matter in Earth is H2O
water (H2O)
Carbon
Abundant
Affinity to link to smaller atoms
Hydrocarbon
propane(C3H8)
Compound of Hydrogen and Carbon
Energy sources
Carbon Dioxide (CO2 )
Carbon Dioxide(CO2)
Isotopes
Isotopes are different types of atoms of the same chemical element, each
having a different number of neutrons
Deuterium
• Hydron atom + 1 neutron
Tritium
• Hydron atom + 2 neutron
Ions
Atom or molecule where the total number of electrons is not equal to the total
number of protons
Anion
• More electrons than protons
Cation
• Less electrons than protons
Quantum physics
Heisenberg Principle
locating a particle in a small region
of space makes the momentum of
the particle uncertain; and
conversely, that measuring the
momentum of a particle precisely
makes the position uncertain.
Quantum mechanics
Explain motion of nuclear particles
(Classical mechanics fail)
Matter as wave
Quantum hydrogen model
Periodic table
Nuclear Plants
Use nuclear energy to produce
electricity using stem cycle
Like thermal plants using coal, oil, gas
4 generations of reactors
Calder Hall
UK (1954)
Waste Flacks
Yucca Mountain
Nevada, US
III – Advanced Boiling Water Reactor (GE)
IV - Very High Temperature Reactor
Generation IV
Fission
Definition
splitting of the nucleus of an atom into parts
forming neutrons and photons (gamma ray)
Radiation
Atoms Loss of energy
Alpha, beta or gamma radiation
Uranium reaction
Fusion
Definition
multiple- like charged atomic nuclei join together to
form a heavier nucleus
Proton-proton chain reaction
Converts hydrogen into helium
Takes 109 years to occur at start’s core temperature
Nuclear Power with fusion
In 1997, JET produced 10MW for 0.5s
ITER in 2018 will produce 500MW for 1000s
Nuclear Energy (SI)
Electro-Volt: 1 eV = 1.602 176 53(14)×10−19 J
JET tokamac
Deuterium-tritium reaction
Hydrogen Fuel
Natural state (H2)
75% of matter (mass) or 90% of mater in
terms of number of atoms
Energy carrier
Production
Water Electrolysis: separate molecules
through electricity (30%-40% efficiency)
Water electrolysis
Storage
Compressed or liquid
Fuel
Filling station
(Germany)
Fuel Cells
Adapted gasoline motor
Hydrogen cell
Toyota FCHV
OPTICS
The nature of light
Light characteristics:
Electromagnetic radiation
Light travels from one point to another
It travels in vacuum (unlike sound, which is an air pressure)
Light transports energy
When we absorb light, it is transformed in heat
Visible Light
Radiation whose wavelength is 380-750x10-9m
Light refraction
(prisma)
Light refraction
(water)
Reflection, refraction
Reflection
Incidence angle=reflection angle
Refraction
Reflection
Mirror
Changes speed and angle of light
Diffraction
Light propagation over small open
obstacles and openings
Refraction
Lens
Thermal solar panels
Flat plate
Evacuated tube
Heating through reflection
Installation diagram
Solar power plant
Almeria, Spain
Photovoltaic panels
PN junction
Photovoltaic panel (PV)
Equivalent circuit