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PHY 1455 Exam #1
| Question | Answer |
|---|---|
| Celestial Sphere | An imaginary great hallow sphere surrounding the earth with stars attached to it. Its a way we identify the stars and where they are. |
| circumpolar star | stars that never set from our position. |
| Polaris | a fairly bright star really close to the North Celestial Pole |
| celestial equator | n imaginary circle around the sky directly above the Earth's equator. It is always 90 degrees from the poles. |
| Declination | The lines on a map of the Earth that run east-west parallel to the equator are lines of latitude that are projected onto the sky |
| Right Ascension | The lines on a map of the Earth that run north-south are lines of longitude and when projected onto the sky |
| lunar eclipse | the Sun-Moon angle is exactly 180 degrees and you see the Earth's shadow covering the Moon. Sun-earth-moon |
| solar eclipse | the moon is in new phase and it is covering up the Sun. Earth-Moon-Sun |
| Annular eclipse | A bright ring will be visible around the Moon when it is lined up with the Sun. (Solar) |
| Retrograde motion | a planet will slow down its eastward drift among the stars, halt, and then back up and head westward for a few weeks or months, then halt and move eastward again |
| Constellations | A way of mapping out the stars in the sky by a group of stars or area of the celestial sphere. |
| Zodiac | Twelve 30 degree divisions on a narrow belt of constellations centered on the ecliptic. You can see one per month. |
| Total eclipse | When the sun is completely covered by the moon because the umbra hits the earth. |
| Partial eclipse | If the Moon only passed through the outer part of the shadow (the penumbra), then the observer on the Moon would see the Sun only partially covered up. |
| Why don't eclipses happen every month? | The orbit of the moon is tilted |
| Zenith | The point straight overhead on the celestial sphere for any observer and is always 90 degrees from the horizon |
| Ecliptic | yearly path of the Sun through the stars |
| Vernal (spring) equinox | When the sun on the ecliptic path intersects the celestial equator moving northward. |
| Autumnal (fall) equinox | When the sun on the ecliptic path intersects the celestial equator moving southward. |
| Summer solstice | when the sun is at the farthest northern point above the celestial equator. |
| Winter solstice | When the sun is at the farthest southern point above the celestial equator. |
| How can you calculate the velocity of light? | Frequency * wavelength |
| Wave nature of light | In a vacuum all waves travel the speed of light |
| Azimuth | how many degrees a star is along the horizon and corresponds to the compass direction |
| altitude | how many degrees a star is above the horizon (anywhere from 0 to 90 degrees) |
| Nadir | The point straight below on the celestial sphere for any observer and is always 90 degrees from the horizon |
| Horizon | The point straight ahead on the celestial sphere for any observer. |
| Electromagnetic waves and examples in order. | Long wavelength (RED) to shortest wavelength (BLUE) - Radio, infrared, visible, ultraviolet, x-ray,gamma-ray |
| Redshift | the object is moving away from you, the waves are stretched out, so their wavelength is longer. The lines are shifted to longer (redder) wavelengths |
| Blueshift | the object is moving toward you, the waves are compressed, so their wavelength is shorter. The lines are shifted to shorter (bluer) wavelengths |
| Blackbody | an object that absorbs all the light falling on it, reflecting none of it, hence, it appears black. When the ``blackbody'' object is heated, it emits light very efficiently without any gaps or breaks in the brightness. |
| What is a spectrum of an object? | The variation in the intensity of its radiation at different wavelengths |
| Absolute zero | When the temperature is at its lowest (0 K) and there is no motion within the molecules |
| Kelvin temperature scale | A natural scale for the temperature that at 0, its the absolute zero. |
| Wien's law | The peak of the thermal spectrum in nanometers is related to the temperature (in K) |
| Stefan-Boltzmann law | A small change in temperature produces a huge change in the amount of the energy emitted by every unit of the object. |
| What gives off a continuous spectrum? | A hot solid, liquid or gas, under high pressure |
| What gives off a emission line spectrum? | A hot gas under low pressure produces a bright-line |
| What gives off a absorption line spectrum (dark lines)? | a source of a continuous spectrum is viewed behind a cool gas under pressure. |
| What do atoms and molecules existence depend on? | Temperature and chemical composition |
| Who made up the spectrum laws? | Kirchhoff |
| Doppler effect | The wave nature of light means there will be a shift in the spectral lines of an object if it is moving |
| Aristotle | He was most associated with the ancient greek world view |
| Aristarchus | rejected the Geocentric world view and supported the Heliocentric view |
| Eratosthenes | accurately determined the size of the Earth |
| Ptolemy | Almagest |
| Geocentric model of the Universe | Where the earth is at the center and things naturally move to the center of the Earth and the only way to deviate from that is to have a force applied to the object |
| Heliocentric model of the Universe | Where the sun is at the center and the planets orbit around it. |
| Copernicus | Invented the Heliocentric model of the Universe |
| Tycho Brache | Last astronomer without a telescope and provided Kepler with the data he needed to create his three laws. |
| J. Kepler | Creates the three laws of planetary motion |
| What is Kepler's first law? | The orbit of a planet is an ellipse where one focus of the ellipse is the sun (Law of Ellipses) |
| What is Kepler's second law? | A line from the planet to the sun sweeps out equal areas in equal amounts of time. (Law of Equal areas) |
| What is Kepler's third law? | The period of a planet's orbit squared is proportional to its average distance from the sun cubed. (Law of harmonies; p^2 = a^3) |
| Gaileo | Used a telescope and challenged the conventional wisdom of the motion of objects and the nature of the heavens |
| What did Gaileo found to challenge Geocentric model? | Phases of Venus and Moons of Jupiter |
| What did Gaileo found to challenge the idea that the heavenly object was perfect? | Sunspots and mountains on the moon |
| Newton | Created the three laws of motion and universal law of gravity |
| What is Newton's first law? | A body remains at rest, or moves in a straight line (at a constant velocity), unless acted upon by a net outside force. (Law of Inertia) |
| What is Newton's second law? | The acceleration of an object is proportional to the force acting upon it. (F=MA) |
| What is Newton's third law? | For every action, there is an equal and opposite reaction. (Law of Reciprocal Actions |
Created by:
atate92
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