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Astronomy Week 3Lite
| Term | Definition |
|---|---|
| spectrum | colors of sunlight spread horizontally |
| visible light | tiny part of electromagnetic spectrum |
| wavelength | distance between adjacent peaks/length of full oscillation of the wave |
| frequency | number of times rope moves up and down each second/of light is the number of wavelengths that pass a certain point in a period of time (dimension: inverse time) |
| speed of light | all light travels through empty space at the same speed wavelength x frequency |
| photons | what light consists of; carries amount of energy that depends on its frequency |
| infrared | light with wavelengths longer than red |
| radio waves | longest-wavelength light |
| microwaves | region near border between infrared and radio waves |
| ultraviolet | light with wavelengths shorter than blue light |
| x rays | shorter wavelength than UV |
| gamma rays | shortest-wavelength light |
| particle radiation | energy carried by particles of matter |
| elements | parts of chemicals, >100, each of a different type of atom |
| radiation | energy carried through space |
| nucleus | center of the atom, composed of positively-charged protons and electrically neutral neutrons |
| electrons | surround nucleus, smaller than protons and neutrons |
| electrical charge | properties of an atom depend on the nucleus' electrical charge. How strongly an object will interact with electromagnetic fields. Always conserved, just like energy |
| strong force | overcomes electrical repulsion and holds nucleus together |
| atomic number | number of protons in its nucleus |
| atomic mass number | combined number of protons and neutrons in an atom |
| isotopes | versions of a element with different numbers of neutrons (same number of protons) |
| molecules | atoms combine |
| emission | light bulb emits visible light; energy of the light comes from electrical potential energy supplied to the bulb |
| absorbtion | when you place your hand near an incandescent bulb, your hand absorbs some of the light, warming your hand |
| transmission | some forms of matter (glass/air) transmit light/allow it to pass through |
| reflection | light can bounce off of matter in same general direction |
| scattering | light can bounce off of matter in the same general direction |
| transparent | material that transmits light |
| opaque | material that absorbs light |
| vision | process; brain interprets the message light carries |
| continuous spectrum | of a lightbulb; spans a range of wavelengths without interruption |
| emission lines | against a black background |
| emission line spectrum | thin/low density cloud of gas |
| absorbtion line spectrum | if a gas cloud is between us and the lightbulb |
| absorbtion lines | visible over background rainbow |
| intensity | amount of light at each wavelength; high=lots of light |
| energy levels | of an atom; only a few are possible |
| ground state | 0 eV |
| excited states | higher energy levels compared to ground state |
| energy level transitions | when an electron's energy level changes |
| ionization level | if gained by electron, escapes atom completely and the atom is left with a positive charge |
| ions | electrically charged atoms |
| thermal radiation | temperature dependence of light |
| Law 1 | Stefan Boltzmann Law: each sq meter of a hotter object's surface emits more light at all wavelengths |
| Law 2 | Wien's Law: hotter objects emit photons with a higher average energy |
| doppler effect | causes shifts in wavelengths of light |
| blueshift | doppler shift of an object coming toward us; bc shorter wavelengths of visible light are bluer |
| redshift | object moving away from us; light shifted to longer wavelengths/redder |
| rest wavelengths | wavelengths in stationary clouds of hydrogen gas |
| radial component | of motion; object's full motion that is directed toward or away from us |
| tangential component | how fast an object is moving across our line of sight |
| solar day | 24 hours |
| sidereal day | 23 hr 56 min |
| summer solstice | highest path, rise and set at most extreme north of due east |
| winter solstice | shortest day, lowest path, rise and set at most extreme south of due east. Sun lowest in the sky. |
| equinoxes | sun rises precisely due east and sets precisely due west |
| precession | slow, circular motion of the Earth's axis of rotation; causes the position of the NCP to change over a period of 26K years |
| apricity | warmth of the Sun on a winter day |
| shorter wavelength | more energy, higher frequency |
| longer wavelength | lower frequency, less energy |
| light-collecting area | of a telescope; determines how much light the telescope can collect at one time |
| angular resolution | amount of detail a telescope allows us to see; smallest angle over which we can tell 2 stars are distinct |
| refracting telescope | uses transparent glass lenses to collect and focus light |
| reflecting telescope | uses curved primary mirror to gather light to a secondary mirror in front of it |
| interferometry | technology, lets multiple telescopes work together to achieve an angular resolution equivalent to a much larger single telescope. Harder for shorter-wavelength light |
| neutrino | lightweight, subatomic particle made by nuclear reactions |
| turbulence | ever-changing motion of air in the atmosphere that bends light in shifting patterns |
| adaptive optics | make telescope mirrors do an opposite dance and computer calculates the changes by monitoring a nearby star's (or an artificial star's) image. Overcomes blurring effects of Earth's atmosphere. |
| luminosity | L=4piR^2sigmaT^4 |
Created by:
mglen
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