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80 Cards in this Set
- Front
- Back
Order of magnitude
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focuses on the exponent, not the actual number
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How far apart is the Earth and the Sun?
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150 million km, or 1 AU
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How far apart are individual galaxies?
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300,000 light years apart
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What is a pulsar?
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A blinking, pulsing light at the center of a recently exploded supernova.
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Where are stars formed?
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stellar nurseries
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What is Earth's diameter?
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13,000 km
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Define planet.
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a small, spherical, nonluminous orbital body
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Define star.
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A self-luminous ball of hot gas generating its own energy.
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What is an asterism?
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a less formally defined grouping of stars
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What is the star nearest to the sun? What is the brightest star in our sky?
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Alpha Centauri; Sirius
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What is flux?
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the measure of the light energy from a star that hits one square meter in one second
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What is precession?
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the top-like motion of Earth that results in the appearance of celestial poles moving across the sky
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What information can astronomers receive from examining a star's light? (6)
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energy output, surface temp, radius, chemical composition, velocity relative to earth, rotation period
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What is the speed of light?
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300 million m/s
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What is a light year?
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the distance light can travel in a year-- 9.46 trillion km
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Name 5 that light is wave-like.
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it has an electromagnetic field, it defracts, it interferes, it reflects, and it refracts
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Name 4 ways that light is particle-like.
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It is made up of photons, it has blackbody radiation, it displays a photoelectric effect, and Compton scattering.
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What is a spectrum?
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a plot of brightness versus wavelength.
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What is a blackbody object?
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An idealized object that doesn't reflect any light, but only radiates it.
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Take note of what is amplitude and what is wavelength.
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okay.
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What is blackbody radiation?
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an electromagnetic spectrum characteristic of an object's temperature
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Radio>>Microwave>>Infrared>>Visible>>Ultraviolet>>X-ray>>Gamma ray. Wavelength (increases or decreases) and frequency (increases or decreases)
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decreases; increases
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What are the two laws of blackbody radiation?
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-the hotter an object, the more energy it emits.
-the peak of the blackbody spectrum decreases (to the left) with increasing temperature. |
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Where is most of the mass of an atom contained?
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in its nucleus
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Explain absorption spectrum/lines.
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Electrons are energized (kicked into a higher orbital level) when it absorbs a photon with just the right amount of energy. When light passes through a cool, low-density gas that absorbs a photon at a unique frequency, the light re-emitted shows up as dark in the spectrum. These lines are absorption lines.
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What are Kirchoff's laws of radiation? 3
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- a solid, liquid, or dense gas excited to emit light will radiate at all wavelengths and produce a continuous spectrum.
- a low-density gas emitting light will do so at specific wavelengths, producing an emission spectrum. - a cool, low-density gas emits light, the result will be an absorption spectrum. |
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Balmer lines of hydrogen:
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Emission or absorption lines that occur from transitions between the second state and higher states of the hydrogen atom.
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Doppler effect:
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sound gets louder when moving toward you and quieter when moving away from you (same thing with the intensity of light; it shifts from red to blue)
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What do optical telescopes do?
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they focus light to gather more than our eyes can see
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What are two types of optical telescopes?
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Refracting and reflecting
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What do refracting telescopes use to focus light?
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a lens
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What is a major disadvantage of a refracting telescope?
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Chromatic aberration (different wavelengths are focused at different focal lengths)
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What do reflecting telescopes use to focus light?
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a mirror
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What four things do telescopes need to work? Describe these things.
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light-gathering power (dependent on surface area), resolving power (minimum angular distance between objects), seeing (clarity), magnifying power (makes image bigger)
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How big do radio waves have to be to penetrate atmosphere and be observed from the ground?
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1 cm - 1 meter
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What is the best location for a telescope?
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Far away from light pollution and high up to minimize atmospheric blurring
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What two principles did early astronomers base their models on that were incorrect?
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Geocentric universe and the "perfect heavens"
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Thales:
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Everything in the universe is made of water.
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Anaximander:
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Earth in the center of the universe was cylindrical, surrounded by a rotating spherical shell of fire with perforations (stars) and two wheels of fire with holes that periodically closed (moon and sun)
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Pythagoras:
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The planets are supported by spheres that rotate around the Earth.
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Plato:
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the heavens are perfect
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Aristotle:
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the sub-lunar realm is changing, imperfect, and made up of four classical elements that have its natural tendency and place. the super lunar realm is perfect and unchanging.
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Why didn't ancient astronomers believe the earth moved?
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They saw no parallax (apparent motion of an object due to the motion of the observer) and observed a retrograde motion of planets.
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How did Ptolemy attempt to explain retrograde motion of planets?
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with epicycles
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Who proposed a heliocentric model for the first time and in what book?
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Copernicus; De Revolutionibus
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Other than the heliocentric model, what else did Copernicus propose? (4)
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- Earth is a planet.
- Earth has 3 kinds of motions: daily, annual, and axis tilting/wobbling. - He explained retrograde motion of planets. -Proposed that the distance between the Earth and the sun is relatively small. |
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What did Brahe and Kepler figure out?
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the motion of mars (flattened ellipse
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What are Kepler's three laws of planetary motion?
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- The orbit of every planet is an ellipse. The semi-major axis is half of the longest diameter of an ellipse.
- Planets move quicker when closer to the sun. - P^2 = a^3 (Planet's orbit period in years and semi major Axis in AU) |
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What are 5 of Galileo's discoveries?
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1. moons of Jupiter
2. rings of saturn 3. moon's texture & structure 4. sun spots 5. places of venus |
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What are Newton's 3 laws of motion?
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1. An object in motion stays in motion unless a force is acted upon it.
2. The acceleration of a body is inversely proportional to its mass, directly proportional to the net force, and in the same direction as the net force. - To every action, there is an equal and opposite reaction. |
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What is acceleration?
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the change of a body's velocity with time
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What are three different cases of acceleration?
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-Increasing speed
- Decreasing speed - Change in direction |
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The acceleration of gravity is ______________ on the mass of the falling object.
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independent
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What is Newton's Universal Law of Gravity?
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Any two bodies are attracting each other through gravitation, with a force proportional to the product of their masses and inversely proportional to the square of their distance.
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What is a geosynchronous orbit?
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An orbit in which an object orbits Earth at exactly the same rate that Earth rotates
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Name four pieces of evidence for the Big Bang.
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- The sky is not blindingly bright
- Galaxies are moving apart - Background radiation is present in all directions in the universe - Hydrogen to Helium ratio is consistent with what is predicted |
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What is Olber's paradox? What is the solution to Olber's paradox?
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If the universe is infinitely old, then every line of sight should end at the surface of a star.
- The universe is finitely old. |
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What is Hubble's law?
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distant galaxies are flying away from us with a speed proportional to distance (father away, faster they go)
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How do we know how far away stars and galaxies are? 5
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parallax, cepheid variable stars, diameter of a globular cluster, characteristic brightness of supernovae from white drawfs, size distribution of galaxies in clusters of galaxies
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What is a parsec?
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3.26 light years; distance between me and another object that makes an angle of one arc second and the base line is 1 AU
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What are Cepheid variable stars?
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They're massive and their variability period is correlated with its luminosity.
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How old is the universe?
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about 14 billion years old
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What is an anti-particle for an electron?
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Positron
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What happens when positron and electron collide?
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they create pure energy and gamma-ray photons.
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What happens when photon and photon collide?
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they create electron and positron again
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What is the recombination period?
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When the universe cooled, protons and neutrons fused together to create helium nuclei and protons electrons fused to form hydrogen atoms.
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What followed the recombination era?
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the dark age
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How old was the universe when the first stars formed?
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less than 1 billion years old
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In what three ways do we classify stars?
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Luminosity, temperature, and size
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How is a star's brightness related to its size?
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Directly proportional
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Know the hertzsprung-russel diagram
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okay.
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Speed of light equation:
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c= fλ
c-- speed of light in meters/s λ--wavelength in meters f--frequency in cycles/s |
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Energy related to frequency equation:
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E=hf
E--energy of photon in Joules h--Planck's constant f--frequency in cycles/s |
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Wien's law describing wavelength of blackbody radiation at its maximum intensity:
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λmax = 2.9*10^6
--------------- T |
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Doppler shift d escribing how the wavelength of light changes if its light is observed from an object moving toward or away from a light source at a radial velocity.
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Δλ = v radial
------ ----------- λ0 c |
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Kepler's third law:
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a^3 = P^2
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Newton's second law:
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F = ma
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Newton's law of gravitation
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F = -GMm
----------- r^2 |
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Newton's laws of motion and gravitation
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4π^2a^3 = GMP^2
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Luminosity, blackbody radiation, and radius equation:
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L = 4πR^2δT^4
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