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| 1,900,000,000,000,000,000,000,000,000 |
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| 0.00000000000000000000000000167 |
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| What do astronomers mean by a “constellation”? |
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| Astronomers divide the sky into 88 contiguous regions called constellations |
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| Define the term Astronomical Unit (AU). |
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| the average distance between the Earth and the Sun. It is approximately equal to 150 million km. |
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The zodiac is the band of sky where the Sun, Moon, and planets are found. There are
12 classical constellations that lie along the zodiac. |
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| Explain why we see different constellations at different times of the year. |
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Definition
We are not able to see the constellations in the region where the Sun appears. Instead, we see the
stars in the direction of the night side of the Earth |
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| Describe how the pointer stars in the Big Dipper are used to find Polaris. |
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Definition
The pointer stars are the two stars at the far end of the bowl from the handle. Motion
along the line defined by these stars, out of the bowl, leads to Polaris—the North Star. |
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Term
Explain what actually moves outward with a water wave that is generated by dropping a pebble
in a pond. |
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Definition
| Wave crests and energy move outward with the wave. |
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| What is electromagnetic radiation? What effect does it have on electrons? |
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Definition
Electromagnetic radiation (light) is a means by which energy is transported through
space as a wave. This wave causes electrons to oscillate back and forth as it passes. |
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| What is the physical significance of the speed of light? |
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| The speed of light (in a vacuum) is the absolute speed limit in the universe. |
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| Wavelength is the distance between successive wavecrests. |
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Frequency is the number of
wavecrests passing a point per time. |
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Amplitude is the height of the wave above the undisturbed
level. |
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Suppose that ocean waves travel at 2 meters per second. If the wavelength is 4 meters, what is the
frequency of the waves? |
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| What is a nanometer (nm)? |
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| A nanometer is one-billionth of a meter. |
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| What is the approximate range of wavelength for visible light? |
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Definition
| 700 nm (red) to 400 nm (violet). |
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| What is a photon? What are its properties? |
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Definition
A photon is the smallest unit of electromagnetic
radiation and cannot be divided. The energy of a photon is proportional to its frequency
and thus inversely proportional to its wavelength. |
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| waves perpendicular to direction, example up and down waves. |
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| waves parallel to direction, example compression wave |
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| types of electromagnetic radiation in order of increasing wavelength. |
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Electromagnetic radiation from shortest to longest wavelength:
gamma-ray, X-ray, ultraviolet, visible, infrared, microwave, radio |
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Term
| Explain how the Kelvin (absolute) temperature scale is defined. |
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Definition
is defined so that its zero corresponds to absolute zero and the degree
size is the same as for the Celsius scale. There are no negative temperatures on the Kelvin scale. |
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| 3 temps of absolute zero? CFK |
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| 3 temps of water freezing point |
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| 3 temps of water boiling point |
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| Explain what black body radiation is. |
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Definition
Black body radiation is produced by an ideal absorber and emitter of electromagnetic
radiation. (perfect smooth spectrum) |
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Definition
spectrum is a separation of light (electromagnetic radiation) into its constituent
wavelengths, using a prism or grating |
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| Why are spectra useful to astronomers |
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Definition
allows astronomers to determine the physical nature of
the object that emits the light, e.g. a gas cloud, star, or galaxy. |
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| a sharp peak or dip in a spectrum at a particular wavelength. |
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| difference between emission and absorption lines. |
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peak
is called an emission line, while a dip is called an absorption line. |
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| What is the relation between the size of an electron orbit in an atom and the energy of the orbit? |
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Definition
| The larger the orbit, the higher its energy. |
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