Waves, the Atom and Optics

Carlos SilvaOctober 14th 2009

WAVES

Vibrations

Definition

Mechanical oscillation around an equilibrium point•Mass-spring system oscillation• Beam• Drum

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

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Period, Frequency and Amplitude

Period (s)

Interval of time measured in seconds that takes to repeat the vibration (T)

Frequency (Hz=s-1)

Number of events/repetitions per second (f)

Wave length (m)

Distance between repeating units

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

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Natural Frequency and Resonance

Natural frequencyProperty of every system

Multiple modes of vibration (harmonics)Multiples of the natural frequency

ResonanceTendency 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

DampingMechanism of energy dissipation of vibration

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www.youtube.com/watch?v=3mclp9QmCGsTakoma bridge:

DampingVibration modes

Waves

Definition

Type of disturbance that propagates through time and spaceWave 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 dualityconcept 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

DefinitionSmallest unit of an element that retains its chemical properties

Greek átomos that stands for indivisible

NucleusProtons (+)

Neutrons

Electrons cloud Electrons(-)

Special orbits

They gain or loose energy while jumping from orbits

Number of protons= number of electrons

Bohr hydrogen (H) model

Oxygen (O) atom

Molecule

MoleculeStable and electrical neutral combination of atoms

Water90% of the matter in Earth is H2O

CarbonAbundant

Affinity to link to smaller atoms

HydrocarbonCompound of Hydrogen and Carbon

Energy sources

Carbon Dioxide (CO2 )

water (H2O)

propane(C3H8)

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 Principlelocating 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 mechanicsExplain 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 reactorsIII – Advanced Boiling Water Reactor (GE)

IV - Very High Temperature Reactor

Calder HallUK (1954)

Waste Flacks Yucca MountainNevada, US

Generation IV

Fission

Definitionsplitting of the nucleus of an atom into parts

forming neutrons and photons (gamma ray)

RadiationAtoms Loss of energy

Alpha, beta or gamma radiation Uranium reaction

Fusion

Definitionmultiple- like charged atomic nuclei join together to

form a heavier nucleus

Proton-proton chain reactionConverts hydrogen into helium

Takes 109 years to occur at start’s core temperature

Nuclear Power with fusionIn 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 carrierProduction

Water Electrolysis: separate molecules through electricity (30%-40% efficiency)

StorageCompressed or liquid

FuelFuel Cells

Adapted gasoline motor

Filling station(Germany)

Hydrogen cell

Toyota FCHV

Water electrolysis

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

ReflectionIncidence angle=reflection angle

RefractionChanges speed and angle of light

DiffractionLight propagation over small open

obstacles and openings

Refraction

Reflection Mirror

Lens

Thermal solar panels

Flat plate

Installation diagram

Heating through reflection

Evacuated tube

Solar power plantAlmeria, Spain

Photovoltaic panels

Photovoltaic panel (PV)

PN junction

Equivalent circuit