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Electromagnetic Energy
Science 30
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Field Lines- Negative charge (having more electrons than protons, Positive charge (having fewer electrons than protons) Understanding a thunderstorm is a great initial way to understand electric field lines and how they interact Water droplets collect at the bottom of storm clouds Because of the polar nature of water, the water droplets hold on to their electrons Thus the bottom of a cloud is negatively charged relative to the top Presence of negative charge on the bottom of the cloud causes a separation of charge at the Earth’s surface A positive charge is induced into the top of the Earth’s surface As rising winds updraft from the Earth due to evaporation they carry positively charged particles with them, this creates attraction between positive protons and negative electrons and thus a pathway for the negative charge in the cloud to be grounded The grounding of charge moving from the cloud to the Earth is what we see as lightning
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Units of Electrons – Coulombs
An SI unit for charge A coulomb is 6.25 x 1018 electrons One coulomb = 1.00 C Objects gaining coulombs are said to -x number C, if an object gains 1 Coulomb it is said to have gained C. BECAUSE ELETRONS are negatively charged Most objects we encounter have less electricity than 1 coulomb q = electron charge, or coulombs C
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Voltage Electrical potential difference, which is the change in potential energy per unit of charge (per coulomb) As units of charge (coulombs of electrons) move from one object to another, they gain potential energy the dissipation of this energy is called the voltage The volt is the unit for describing electric potential difference, 1V = 1 J/C It is the difference in electrons between two objects (or between membranes) in the relationship to the amount of electrons present in the situation Voltage = Energy or Work / Charge
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Energy and Charge Voltage indicates the joules of energy transferred by every coulomb of charge Two indicate level of voltage: 1) More coulombs = larger voltage 2) Bigger difference in coulombs between two objects = larger voltage Something that is high voltage has A LOT OF COULOMBS and the difference between its coulombs and something is important exchanging coulombs between two high voltage objects for example will not cause a big dissipation of energy because the difference is not that great
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The Electric Field An electric field is a property of the space around a source charge that enables the source charge to exert forces on other charges that enter this region Any charged object has an electric field We can detect electric fields by using test bodies, which is anything that experiences a force due to the presence of a field In a thunderstorm you can often feel the electric field of a storm cloud before lightning strikes
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Field Line Density – More C = more electrons present, thus higher voltage object
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Direction and Electric Fields
Direction of an electric field line is always determined by the direction of the force on a positive test body A positive test charge leaves a positive source and moves towards a negative source This is why electric field lines point away from a positive test source and towards a negative test source
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Thundercloud Field Lines – this is why you seek low ground in a thunderstorm
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Magnetic Field A property of the space around a magnet or electric current that enables the magnet or electric current to exert forces on other magnets, such as compass needles, and electric currents that enter this region A moving electric current creates its own perpendicular magnetic field Moving charge always move from a magnetic north to south pole
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Electromagnetism Moving electrons create electric current, they also create a magnetic field Electrons flow (they exist outside the nucleus of atoms), they also have angular momentum (or a spin) The flow causes electricity, the angular momentum due to the spin causes a magnetic moment When moving, electron flow causes magnetism due to the angular momentum electromagnets due not have magnetic properties if electrons are not moving In this case, think of electrons a flowing loop of charge, they are not only moving, they are spinning at the same time, each movement creates its own properties
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Electromagnet
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Ferromagnetism Some objects not moving also have magnetic properties
Horseshoe magnets are objects that contain metals with magnetic properties, like Iron Metals with magnetic properties have areas on them called domains, regions where particles interact together In the presence of a strong magnetic field, these domains will align, giving the substance magnetic properties The protons and the electrons in a ferromagnet are influenced by the angular momentum of an applied magnetic field Any MOVING CHARGE WILL CREATE A MAGNETIC FIELD, a mmoving charge is called a CURRENT
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Earth’s Magnetic Field
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Earth’s Magnetic Field
Is a result of moving charges Earth has a liquid outer core, which contains electrons, which can move Layers of charge can build up as a result, as Earth spins on its axis this liquid outer core creates a terrestrial magnetic field Here’s the crazy thing, compass needles always point toward the south pole of a magnet (charge moves there) The magnetic south pole of Earth is actually in the Northern Hemisphere, so when a compass north, it is pointing to OUR GEOGRAPHICAL NORTH, but it is actually pointing to its magnetic south pole
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Earth’s Magnetic Poles
Earth’s magnetic poles flip on average every years, however there is a really large diversity with when this happens The last major flip was years ago but their was a smaller one only years ago Earth’s magnetic field is created by moving charge from molten iron and other metals flowing in the core Coriolis forces causing deflection of flowing particles due to Earth’s spherical nature and rotation on its axis also influence fluid dynamics of the molten outer core Disturbances such as plate tectonic shifting or celestial impacts can disrupt the electric currents in the core, causing pole flips Also over time, the field lines can become twisted due to Coriolis forces, this weakens field strength, and can cause the lines to “break”, they realign over time and may flip
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Earth’s Magnetic Field – A Protective Shield
Earth’s magnetic field protects us from cosmic rays and solar winds It deflects most high energy ions so our bodies are not bombarded with charged particles Both cosmic rays (high-speed, ionized particles ejected from objects beyond the solar system) and solar winds (high speed, ionized particles from the Sun, contains electrons, protons, and Helium nuclei) contain high amounts of electrons and protons Some of the solar wind gets through the magnetic field through polar cusps If solar winds get into the atmosphere they collide with atmospheric particles and cause the Aurora Borealis
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Solar Winds – Aurora Borealis
If electrons from solar winds collide with nitrogen, purple light is emitted Red and green light is emitted with collisions with oxygen Solar winds that are exceptionally strong can mess up Earth’s magnetic field, it disrupts compasses and GPS satellites, and can also cause power surges and blackouts
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Gravitational Fields Gravity is a universal force of attraction between all matter in the universe It is a force that needs to be considered along with electricity and magnetism A gravitational field is a property of the space around a source mass that enables the source mass to exert forces on other masses that enter the region Gravity is dependent on mass. If an object has more mass, it has more of a gravitational force this determines orbits, and structures of all objects in the universe
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Field Equations – Gravitational Field Strength
Gravitational field strength is the number of Newtons per kilogram a test body will experience at a given location from a source mass g = gravitational field strength (N/kg) Varies dependent on object we are considering G = gravitational constant = 6.67 x N.m2/kg2 m = mass of source (kg) r2 = distance from center of source (m)
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Field Equations – Gravitational Force
The force exerted on a test body by a gravitational field; calculated by multiplying the mass of the test body by the gravitational field strength Measured in Newtons m = kg g = N/kg Acceleration due to gravity on Earth = m/s2
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Electric Field Strength
Number of Newtons per coulomb that a test body will experience at a given location from a source charge E = electric field strength (N/C), expressed as a vector and an absolute value k = coulomb constant = 8.99 x 109 N.m2/C2 C = charge on source, in coulombs r = distance from center of source (m) ELECTRIC FIELD STRENGTHS ARE GREATER THAN GRAVITATIONAL FIELD STRENGTHS, unless an object is really big, this is why the coulomb constant is so large
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Electric Force Force exerted on a charged test body by an electric field; calculated by multiplying the electric field strength by the charge on the test body Fe = electric force = measured in Newtons (N) Fe = Eq
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Charges Need to Be Grounded
Or connected to the ground with a conducting material Safe conducting path needed for stray or excess charge The ground would have zero electric potential energy, thus cannot conduct stray charge to an unwanted spot
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Motors and Generators Electrical Energy – energy made available by the movement of charge Mechanical energy – the energy possessed by an observable object due to motion or its position; the sum of the kinetic energy and potential energy of an object Em = Ep + Ek Electrical energy is tough to measure directly because it is not directly observable, we see it when it is converted to other forms of energy like sound, light, thermal, kinetic, or mechanical energy The electric motor is a good place to look at energy conversions because mechanical energy can be measured
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Electric Motors An electric motor has the following features:
Armature – the part that spins, has a coil of wire, a rotating shaft and a commutator Commutator – provides electrical contact, allowing current to flow to the rotating coil Shaft – supports the coil of the armature, providing an axis for the rotation of the armature Does the mechanical work the motor was supposed to do (like move a wheel axle, turn a turbine etc) Brush – a stationary part of a motor or generator that makes electrical contact with the rotating commutator Electricity enters the armature through the brushes
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Electric Current in Motors
How much current flows through an electric motor or electricial device is expressed as A = amperes, or amps… 1 amp = 1 coulomb/1 second
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Current Traveling Through Motors and Generators
Generator – An object that produces electrical energy for mechanical energy DC – Direct Current – a flow of charge that is constant and does not change direction AC – Alternating Current – a flow of charge that reverses direction at regular intervals AC generators use electromagnets to create energy, as the armature flows through a magnetic field you get alternating currents
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AC Generator Electron flow flips as the current moves through the magnetic poles (electrons always flow from north to south) As the coil rotates, the positive and negative terminals flip and electron flow reverses
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AC vs DC Generator In AC Generators, the SLIP RING commutators are split (called slip rings), this keeps the brushes separate so current can alternate In DC generators, SPLIT RING commutators cover the wire coils on the armature in one casing. This allows a constant, consistent, single direction flow
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Why AC, not DC for Power Generation?
Signal transmission weakens significantly with power transmission in DC generators, the further away from a power station you get the less power you receive AC power generation is also easier to control, DC can be quite dangerous because of the buildup of charge AC power can easily be restored over reinforced within transformers along the power grid
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Importance of Generators
Generators are needed as the first step in creating all power generation that fuel the modern world 4 things are needed to maximize power generation: Lots of wire turns on the armature Armature spinning quickly Strong magnets Iron core
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Electric Circuits Series Connector- single path available for electric current, charges flow from one device to the next Parallel Connector – more than one available path for the electric current, where electric current divides, allowing each portion of the current to simultaneously pass through separate devices
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Circuit Symbols – see pg. 374
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Measurements Voltmeter – measures voltage across two point in a circuit Ammeter – measures electric current flowing through a component in a circuit Ohmmeter – measure resistance in a circuit A multimeter can measure multiple things in a circuit
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Multimeter Measuring current (amps) – set the multimeter to 200mA (milli- amperes) Measuring Voltage (Volts) – set the multimeter to 20V Measuring Resistance (ohms) – set multimeter to 2000 ohms (2k)
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Resistance The ratio of the voltage across a device to the current flowing through it Resistor – an electronic component that resists the flow of electric current in a circuit, any object that a current has to pass through in a circuit is a resistor to current flow Thus bigger voltages are needed as the amount of resistors increases in number or size Resistance = ohms = volts/amperes = V/I
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Ohm’s Law Ohm discovered that some materials maintain a constant ratio of voltage to current, it is a good measure for predicting the behavior of conductive material
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Calculating Total Resistance
Series, top equation Only one path for the bulbs to follow Moving charge has to overcome the resistance of every bulb connected in series Thus the total resistance is the sum of the individual resistances Parallel, bottom equation - having additional paths allows more current to flow - therefore as more pathways for current are added, resistance diminishes - thus resistance diminishes as resistors are added, leading to total resistance being the inverse sum of the resistors
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Household Wiring – a combination of series and parallel circuits
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Electrical Transmission
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Power A quantity used to describe the rate of doing work, or transforming energy into something useful energy used over a given duration of time NOT necessarily referring to electrical systems However, the goal of electrical devices is to produce the required quantity of useful energy while consuming the minimal quantity of electrical energy P = power = watts (W) = J/s W = work or energy = Joules (J) t = time = seconds (s)
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Kilowatt Hours – Price of Electricity
W = E = P*t For utilities bills, power is measured in Kilowatts Time is measured in hours We multiply the amount of kilowatts per hour to determine electrical utility rates 1kW*h = 3.6 x 106 J Current Utility Rates as of December 2014 in Calgary were 7.29 Cents per kW*h
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Power in Electrical Systems
When dealing with electrical systems, power is a function of the voltage of an object multiplied by the current it sustains P=VI = (J/C) * (C/s) = J/s = WATTS The power of electrical circuits are described using this relationship
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Resistance Also Determines Power
If voltage isn’t given, we know that V=IR P=VI, thus P=(IR)I, you can substitute variables for voltage into the power equation
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Where Electricity Comes from In Alberta
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Where Power is Lost Most power in electrical transmission is lost in the heat produced by electric current passing through conducting cables Thus the resistance in electrical cables is reduced as much as possible by using highly conductive materials and good insulators to prevent useless energy conversion P = I2R
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Transformers A device that transforms the AC voltage of one circuit into a different AC voltage for another circuit using separate coils of wire wound around a common iron core
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Components of a Transformer
A transformer has a primary coil and a secondary coil wrapped around a central iron core The primary coil receives the input voltage from an applied electrical force The secondary coil supplies the output voltage of a transformer
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Transformer
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Transformers Step-up transformers INCREASE the voltage of an electrical current from one coil to another Step-down transformers DECREASE the voltage of an electrical current from one coil to another
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How it Works If a current within a primary coil is changing (ie- AC current), a magnetic field can be induced into the iron core of the transformer If you close the switch on the primary coil you can increase the magnetic field in the iron core, and induce current into the secondary coil Current will be increased to the secondary coil by closing a switch and decreased by opening the switch HOWEVER, biggest factor determining if a transformer is STEP UP or STEP DOWN is the coiling ratio between primary and secondary coils
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How it Works Step Up Step Down
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Coiling Increasing the amount of coils on the secondary coil creates A STEP UP TRANSFORMER, this increases the voltage of the output current, great for transmitting electrical energy from a power station large distances across power lines Decreasing the amount of coils on the secondary coil creates a STEP DOWN TRANSFORMER, this decreases the voltage of the output current, this is great when we transfer high voltage transmission electricity from the power grid to households, if houses were to receive high voltage electricity directly from the grid household circuitry would be continually blown out
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Transformers, Power In = Power Out
Because energy cannot be created or destroyed, there has to be a balance between current and voltage as the number of coils change in transformers In a step-up transformer, voltage increases in the secondary coil in comparison to the primary coil (there is a bigger difference in coulombs between coils), current decreases however In step-down transformers, voltage declines but current increases, thus there is more of an equal distribution of electrons between primary and secondary coils, there are less coulombs being transferred to the secondary coil
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Ideal Transformer Equation – V=voltage, N=number of coils, I=current, P and S = primary and secondary coils
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The Electromagnetic Spectrum
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Electromagnetic Radiation
Or EMR, is a wave that consists of a changing electric field and a changing magnetic field traveling at right angles to one another Energy not sent through vibration, oscillating fields creates it Originates from accelerating charges Radiation – energy emitted in the form of particles or waves
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Describing Radiation EMR is a transverse wave, vibrations of the wave are perpendicular to the direction the wave is traveling One cycle of a wave has a crest and a trough a cycle is one complete vibration of a wave In one cycle is a wavelength the distance from a point on one wave to the corresponding point on the next wave, length of one wave cycle
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Symbol for Wavelength = Lambda
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Frequency Measured in Hertz (Hz), the number of cycles a wave circulates per second More vibration, higher frequency
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Universal Wave Equation
Frequency multiplied by wavelength gives you an accurate description of the speed of a wave, this can be applied to all types of waves HOWEVER, when dealing with Electromagnetic radiation, the speed of the wave never changes, an electromagnetic wave always travels at the speed of light, 3.0x108 m/s = c We depict electromagnetic wave equations as c = f * lambda
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The Electromagnetic Spectrum
Wide band of different types of electromagnetic radiation ranging from radio waves to gamma rays It is important to understand the relationship between frequency, wavelength, and energy of waves Higher frequency = shorter wavelength, higher energy Lower frequency = longer wavelength, lower energy High frequency radiation can penetrate inside living tissue because it is small, and can damage cells, DNA, and affect cellular growth as a result
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Radiowaves Lowest frequency, produced by low-frequency vibrations of electrons within electric circuits Frequency less than 3000GHz, used for communications = 3.0 x 1012 Hz Antenna – transmit or receive electromagnetic energy in the form of radiowaves ELF – extremely low frequency radiation, between Hz, comes from power lines and household appliances, sometimes called background radiation MRI – Magnetic Resonance Imaging – radiowaves with length of about 4m, used with strong magnetic fields to create body images. Radiowaves cause hydrogen atoms in body tissues (soft and hard) to give off energy, this energy can create an image
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Microwaves Electromagnetic radiation with a frequency between 1GHz and 100GHz (1.0 x 109 Hz – 1.0 x 1011 Hz) Used for satellite, communications, and cooking food There is some overlap with radiowave frequency, but generally transmit more energy BUT HAVE SOME OF THE SAME FUNCTIONS Low frequency microwaves used for cooking cause an increase in the molecular motion of water molecules, increasing temperature Higher frequency microwaves used in telecommunications (penetrate through precipitation)
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Infrared Radiation Electromagnetic radiation with a frequency between 3.0 x 1011 Hz and 4.3 x 1014 Hz, increases vibrations between molecules, experienced as heat Just below red light Infrared can BE BEAMED between wireless devices to send encoded wireless signals
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Infrared Beaming – smart devices
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Visible Light Complete range of all colors of light that can be seen by the human eye ROYGBIV Frequencies range from 4.3x1014 Hz – 7.5x1014 Hz Red wavelengths are about 700nm and violet wavelengths are about 400nm, we see a small snippet of the spectrum Visible light actually travels as PACKETS of energy, called photons these photons are quantum matter that act as both a wave and a particle depending on the circumstances this is the WAVE_PARTICLE Duality of Nature
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Photons and Photosynthesis
ROYBIV packets of light are absorbed by chloroplasts to liberate electrons to make energy This energy helps drive the synthesis of glucose Green (G in ROYGBIV) are not absorbed, they are reflected, which is why most chloroplasts look green. Green wavelengths of light do not liberate electrons, thus they are released giving plants the appearance of green (most of them anyway) Different plants have different types of photosynthetic pigment depending on the wavelengths of light they absorb and reflect
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Ultraviolet Radiation (UV)
“ultra” means beyond, UV is beyond the visible light spectrum Electromagnetic radiation emitted by very hot objects (like the sun), frequencies range from 7.5 x 1014 Hz – 1.0 x 1018 Hz 400nm-100nm wavelength UVA – nm – can wrinkle skin, possible skin cancer UVB – nm – sunburn, skin cancer, cataracts UVC – nm – ionizing radiation, breaks chemical bonds, DNA mutation and cancer Earth’s OZONE layer absorbs this IONIZING RADIATION – very energy particles can pass through matter and eject atoms and electrons, creating ions in tissue these ejected are FREE RADICALS, free radicals can destroy DNA and other living tissues UV has a wide range of uses including sterilization, forensics, LED’s, lasers, photography, creating vitamin D in our bodies
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X Rays High energy electromagnetic radiation with a frequency between 1018 and 1021 Hz, can be produced when fast-moving electrons strike a metal target Emitted naturally, large, dense, hot celestial objects Powerful form of ionizing radiation
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How X Rays Work X rays react with photographic film to create light and dark images Dense tissues absorb more photons, thus more energy, and appear lighter on an x ray exposure Less dense tissues appear darker X rays are produced by a high voltage tube, this gives electrons high speeds, they hit a metal target in the tube, producing xrays, xrays emitted to tissue after electrons collide with metal When xrays collide with living tissue, it causes ionizing radiation, knocking an electron out of the tissue The xrays create the ionizing radiation and the radiation reacts with the film in the xrays tube, creating an image
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Gamma Rays High energy form of electromagnetic radiation from frequencies above Hz, emitted from radioactive materials Radioactive is a term used to describe substances that emit radiation from unstable nuclei Very similar to x-rays but emitted spontaneously Radiation therapy can use gamma, x- rays, or UV to combat cancer growth
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The Polygon - Kazakhstan
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Astronomy – science of objects and phenomena that originate outside Earth’s atmosphere
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EMR and Space We are primarily knowledgeable about the universe beyond Earth through the study of EMR we receive from distant celestial objects The Sun is our closest star, at its core, it is fueled by a process called nuclear fusion FUSION happens when two smaller nuclei join to form a larger nucleus, this releases massive amounts of energy The Sun’s core is oC, fusion can only happen at extreme temperatures like this 2 heavy isotopes of hydrogen, called deuterium react with each other to produce Helium, a neutron and energy is released in this process Energy is released as gamma radiation
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The Sun’s Energy Profile
Gamma radiation is released as photons, as these photons are emitted, they collide with particles outside of the core As these gamma photons collide with particles on their way out the Sun, they lose energy, the radiation is converted to UV and infrared radiation, hence why the Sun’s surface is only about 6000oC Solar flares still emit X-rays and gamma rays, realignment of the Sun’s magnetic field create these flares The Sun emits radiation from the entire EMR spectrum, most radiation from the Sun is absorbed by Earth’s atmosphere, solar wind particles create the Aurora Borealis
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Properties of Visible Light
Light travels in straight lines Light can be reflected Light bends (refraction and diffraction) Light is a form of energy
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Refraction – Sundogs Light bends, ice crystals in the air create Sundogs on cold days in the winter Sun is low in the atmosphere in the winter, this permits more bending of sunlight during the winter season
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Light Bending – Refraction
The bending of light due to its change in speed as it moves through different substances Speed of light in a vacuum is km/s or 3.0 x 108 m/s The speed of light changes (slows down) as it moves through denser media (a vacuum has no particles and therefore 0 density)
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Refraction Explained If light hits an object at an angle, it bends
It slows down as it moves through a dense medium and bends towards “the normal” It speeds up as it moves from a dense medium to a less dense medium and bends away from “the normal”
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Galileo’s Refracting Telescope
Galileo created a very primitive telescope that observed the craters of the moon, moons of Jupiter, and rings of Saturn, simply by using a combination of a convex and concave lens Light diffracting was Galileo’s biggest problem with his telescope Diffraction is the bending of waves as it passes by obstacles or through an opening Galileo’s telescope had a very small opening, and as a result seeing objects that were close together was difficult Light moving through small openings create DIFFRACTION PATTERNS, this is why it is hard to see objects further away with your eyes
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Diffraction Patterns
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Reflection A return of a wave from a boundary
Wave bouncing off boundary bounces off at the same angle Polarization – EMR waves can oscillate in more than one direction, the electric and magnetic field propagate perpendicular to the direction of travel, but on different planes In winter and on sunny days, direct and reflected sunlight can enter your eyes Polarized lenses can cut out one of the oscillating orientations of EMR, effectively only allowing light to vibrate in one orientation Polarized Lenses
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Polarization Effect
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Law of Reflection When a ray hits a mirror, it bounces off the mirror at EXACTLY the same angle The line perpendicular to the point of reflection is called the NORMAL The angle between incident ray and the normal is the ANGLE OF INCIDENCE The angle between the reflected ray and the normal is ANGLE OF REFLECTION
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Newton’s Reflecting Telescope
Large circular mirror that curves inward Curved surface gathers light while another mirror directs light to the eyepiece (which is a convex lens) TWO ADVANTAGES OVER REFRACTING TELESCOPE Lens can have a same effect as a prism, distorting light through refraction, mirrors do not do this Reflecting telescopes can be made with large openings because curved mirror is supported underneath the opening, this solves the diffraction problem
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Modern Reflecting Telescope
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Multi-wavelength Astronomy
In reality, astronomy is done studying the nature of EMR entering our atmosphere from space Different wavelengths reveal different information about the universe
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Studying EMR We can study the energy content, wavelength, frequency, degree of polarization, and speed of all EMR in the Electromagnetic Spectrum Waves properties dominate at the lower of the spectrum Photon properties dominate at the higher end of the spectrum
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Analyzing Starlight To observe starlight, when light is collected in a telescope, we can use a diffraction grating to separate visible light to create a spectra for analysis, a diffraction grating is a piece of glass or plastic etched with tightly spaced parallel lines on its surface Anything that is dense material heated to about 6000oC will produce a continuous spectrum, no distinct lines over the emission spectrum are shown, unbroken band of wavelengths
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Spectral Lines
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Absorption Spectrum A dark-line spectrum, has a pattern of dark lines due to the light passing through an absorbing medium, used to identify materials Dark lines are radiation lines that have been absorbed Atoms of a particular element in a low pressure gas will only absorb certain wavelengths Acts like a fingerprint, allows astronomers to determine the components of celestial objects
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Emission Spectrum Or bright line spectrum, takes absorption spectrum one step further when an electric current is forced to pass through a low pressure gas (gas is heated up and emits light) This reverses the effect of the absorption spectrum, the wavelengths that the gas absorbs in the absorption spectrum are emitted when brought to a higher energy level Only certain wavelengths are emitted rather than certain lengths being absorbed A device with a diffraction grating analyzes these spectra, this device is called SPECTROMETER
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Spectra Tell Us About Components of Stellar Objects
Astronomers analyze the chemical composition of clouds of gas around stars, star forming regions, and around planets This tells us how stars, galaxies, and solar systems form and also tells us how these large objects move
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Hydrogen Spectra
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Emission Lines – we can put multiple emission spectrums together to determine the contents of stellar objects
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Doppler Shift The Doppler Effect is a change in the observed frequency of a wave due to relative motion between the source and the observer We generally observe the Doppler Effect in relation to sound However it has large implications for astronomy Due to relative motion, objects observed in the universe that are moving toward us are seen as BLUE-SHIFTED, the EMR we receive appears to be a higher frequency because the waves are bunched closer together Object moving away from us are considered RED-SHIFTED, we receive lower frequency visible light due to Doppler Effect, ALMOST ALL OBJECTS ARE RAPIDLY MOVING AWAY FROM US VERY RAPIDLY and thus we receive red-shifted light This proves the universe is expanding and gives us evidence of the Big Bang
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Doppler Shift
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Star Classification Low-Mass Stars Intermediate-Mass Stars
High-Mass Stars
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Low-Mass Star Evolution
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Intermediate-Mass and High-Mass Star
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Low-Mass Star The Sun is a low mass star, less than 1.4 times the mass of the Sun is a low-mass star Core up to oC Gravitational forces causes gas and dust to collect, turning into a low mass star (the Sun is there now) Once fusion causes gas at core to exhaust, core collapses, outer portions expand, RED GIANT created Core temperature rises and outer layers are puffed out as a nebula and separate from core What is left over will be a dense white dwarf Because there is less mass, fuel is burned slowly, low-mass stars have a longer life-span than intermediate and high mass stars (billions as opposed millions of years) Sun has a life span of about 9 billion years
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Low-Mass Evolution terms
Red Giant – star of great size and age, has a relatively low surface temperature Nebula – an interstellar cloud of gas and dust formed after red giant puffs off its outer portion
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White Dwarf – compact star found as the last stage in the evolution of low-mass stars
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Intermediate-Mass Stars
1.4 and 8 times the Sun’s mass Stellar evolution happens more quickly Core is oC Lifespan could hundreds of millions to a few billion years Gas and dust swarm, gravitational forces create intermediate-mass stars, intermediate-mass star puffs up to a Supergiant, star collapses quickly once fuel is used up Rebound explosion from collapse creates a Supernova, intermediate-mass stars end up as neutron stars some develop into pulsars
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Intermediate Mass Star Terms
Supernova – stellar explosion that produces a very bright cloud of ionized gas that remains a very bright object in the sky for weeks to months Neutron Star – super dense star consisting mainly of neutrons formed as the stage in the stellar evolution of intermediate-mass stars
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Pulsar – rotating neutron star that emits radio waves in pulses
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High-Mass Star Evolution
Greater than 8 solar masses Could live as short as 1 million years, burns fuel extremely fast When a core of a High-Mass Star implodes as the fuel is spent, a supernova does not occur, the core continues to collapse becoming more dense Gravitational field is eventually so dense that light cannot escape, this is a black hole EMR not emitted, it is absorbed so it will be detected by an absence of EMR in a portion of space
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High-Mass Star Terms Collapsing Star
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Black Hole – Last Stage in High-Mass Star Evolution
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