1. Electromagnetic Energy
Science 30

2. 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

3. 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

4. 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

5. 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

6. 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

7. Field Line Density – More C = more electrons present, thus higher voltage object

8. 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

9. Thundercloud Field Lines – this is why you seek low ground in a thunderstorm

10. 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

11. 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

12. Electromagnet

13. 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

14. Earth’s Magnetic Field

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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)

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. Circuit Symbols – see pg. 374

35. 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

36. 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)

37. 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

38. 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

39. 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

40. Household Wiring – a combination of series and parallel circuits

41. Electrical Transmission

42. 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)

43. 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

44. 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

45. 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

46. Where Electricity Comes from In Alberta

47. 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

48. 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

49. 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

50. Transformer

51. 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

52. 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

53. How it Works
Step Up
Step Down

54. 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

55. 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

56. Ideal Transformer Equation – V=voltage, N=number of coils, I=current, P and S = primary and secondary coils

57. The Electromagnetic Spectrum

58. 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

59. 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

60. Symbol for Wavelength = Lambda

61. Frequency
Measured in Hertz (Hz), the number of cycles a wave circulates per second
More vibration, higher frequency

62. 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

63. 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

64. 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

65. 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)

66. 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

67. Infrared Beaming – smart devices

68. 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

69. 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

70. 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

71. 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

72. 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

73. 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

74. The Polygon - Kazakhstan

75. Astronomy – science of objects and phenomena that originate outside Earth’s atmosphere

76. 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

77. 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

78. Properties of Visible Light
Light travels in straight lines
Light can be reflected
Light bends (refraction and diffraction)
Light is a form of energy

79. 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

80. 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)

81. 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”

82. 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

83. Diffraction Patterns

84. 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

85. Polarization Effect

86. 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

87. 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

88. Modern Reflecting Telescope

89. 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

90. 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

91. 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

92. Spectral Lines

93. 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

94. 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

95. 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

96. Hydrogen Spectra

97. Emission Lines – we can put multiple emission spectrums together to determine the contents of stellar objects

98. 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

99. Doppler Shift

100. Star Classification Low-Mass Stars Intermediate-Mass Stars
High-Mass Stars

101. Low-Mass Star Evolution

102. Intermediate-Mass and High-Mass Star

103. 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

104. 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

105. White Dwarf – compact star found as the last stage in the evolution of low-mass stars

106. 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

107. 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

108. Pulsar – rotating neutron star that emits radio waves in pulses

109. 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

110. High-Mass Star Terms
Collapsing Star

111. Black Hole – Last Stage in High-Mass Star Evolution