Astronomy 120 Winter 2005 Highlights of Astronomy. First Midterm Examination

Transcription

1 Astronomy 120 Winter 2005 Highlights of Astronomy First Midterm Examination Name: MULTIPLE CHOICE: Choose the one best answer from among the five choices for each of the following 6 questions. Each correct answer is worth two points. 1. If you see a star rise due East, pass through the zenith (i.e. directly overhead) and then set due West, you know that your latitude is: (A) 90 degrees South (South Pole) (B) 45 degrees South (C) 0 degrees (Equator) (D) 45 degrees North (E) 90 degrees North (North Pole) 2. If, on December 21 st, you observe that the Sun never rises and never sets, but instead just circles around the sky, at a constant elevation above the horizon, then you know that your latitude equals: (A) 90 degrees South (South Pole) (B) 45 degrees South (C) 0 degrees (Equator) (D) 45 degrees North (E) 90 degrees North (North Pole) 3. When the Sun is in Gemini, the constellation Gemini can be seen: (A) starting just after sunset, and until midnight (B) all night (C) starting just after midnight, and until sunrise (D) starting after 3 AM, and until sunrise (E) none of the above 4. One night, around midnight, you observe a Moon that is exactly half-lit and half-dark. It is very near the Eastern horizon. It must be: (A) a New Moon (B) a First-Quarter Moon (C) a Last-Quarter Moon (D) a Full Moon (E) a Waxing Crescent Moon 5. How long does it take for the Sun to make one full trip along the ecliptic ( Zodiac path ), thus visiting each of the 12 Zodiac constellations? (A) one sidereal day (B) one solar day (C) one sidereal month (D) one year (E) 26,000 years 6. If the velocity of an object is constant then we can conclude that: (A) the acceleration of the object is constant (B) the acceleration of the object is zero (C) the sum of all the forces acting on the object (the net force ) is zero (D) B and C (E) A and C

2 THE CELESTIAL SPHERE: The next four questions relate to the celestial sphere, pictured below. Each correct answer is worth three points. 7. Draw the position of the constellation called the Southern Cross on the above picture of the celestial sphere. 8. For an observer at the equator, at what time of year will the constellation Gemini be visible during almost the entire night? 9. For an observer at the equator, at what time of year will you be able to see a Full Moon in Sagittarius? 10. For an observer at the equator, at what time of year will you be able to see a Full Moon in the Southern Cross?

3 FILL IN THE BLANK(S): For each of the following ten statements, insert the most appropriate word or phrase in the space(s) provided. Each statement is worth a total of four points. 11. In the heliocentric theory, the Earth orbits the. 12. The heliocentric theory was proposed in the sixteenth century by _. 13. Early in the 17th century, using an invention called the that had recently been invented in Holland, the Italian astronomer _ discovered the phases of and the moons of _. 14. Consider the Celestial Sphere picture: As the Celestial Sphere rotates from East to West, the Sun and Moon are attached to the Celestial Sphere but slowly move Eastwards along the Celestial Sphere; while the superior planets also generally move Eastwards along the Celestial Sphere, except when they are executing motion. 15. Around the year 1800, the English physicist Young did experiments that showed that light exhibited the phenomenon known as interference, thus proving that light is a (write wave or particle ). 16. One of the key ideas of the branch of physics known as mechanics, that was developed early in the twentieth century, is that everything has both wave and particle properties. 17. Of the five naked eye planets, the two that will never be seen to rise at sunset are _ and _. 18. When an object is moving along a circular path at a constant speed this is referred to by physicists as. 19. A Solar Eclipse can only occur when the Moon is in its Moon phase. 20. Using the fact that a radio wave having a wavelength of 3 meters has a frequency of 100 MegaHertz, we can determine that a radio wave having a wavelength of 12 meters must have a frequency of MegaHertz.

4 SHORT ANSWER QUESTIONS: For each of the following three questions, provide a brief answer in the space provided. Each question is worth 12 points. 21. Over a long period of time extending approximately from the eighth century through the fifteenth century, Islamic astronomers made very important contributions to astronomy. Discuss these. 22. During the Hellenistic period, the Greek Eratosthenes was able to accurately determine the size of the Earth by observing how the elevation of the Sun above the horizon at Noon on the longest day of the year changes with latitude. Explain how other Greeks living during the Hellenistic period were able to use this measurement of the size of the Earth to determine the distance to the Moon.

5 23. The vibrations of a plucked guitar string can be thought of as being composed of a series of many different standing waves, or modes, where each such mode has a definite wavelength and therefore a definite frequency. Make a sketch showing a guitar string and showing just one of the standing waves or modes: Specifically, show the mode that has the lowest frequency. If the length of the guitar string is one meter, what is the wavelength of this mode?