Physical Elements (Geography 1) Name: ______Homework #1: EarthSun Relations DUE: ______Circle Class period: 7:45 am 9:30 am 11:15 am
Earth-Sun Relations Homework (Refer to the diagram below and Figures 1‐25, 1‐26, and 1‐27 on pages 20‐21 of the text.)
1. What is the latitude of the most direct rays of the Sun on June 21? Text p. 20‐21 ______
2. What is the latitude of the tangent rays of the Sun in the Northern Hemisphere on June 21st? (These are the northernmost rays that just barely touch the Earth – the dashed lines in the sketch to the right.)
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3. What is the latitude of the tangent rays in the Southern Hemisphere on June 21st?
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4. Why is the June solstice associated with Northern Hemisphere summer?
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Notice the orientation of the Circle of Illumination on June 21st. 5. Does the equator receive more day or night on this day?
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6. Does day become longer or shorter as you move southward from the equator?
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7. a) How many hours of daylight are experienced between 66.5ºN – 90º N on June 21?
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b) Why?
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Solar Angle
The direct (or overhead) rays of the Sun will strike the Earth’s surface at the Tropic of Cancer (23.5ºN) on June 21, at the equator on the equinoxes, and at the Tropic of Capricorn (23.5ºS) on December 21. The latitude of these direct rays is called the declination of the Sun or the subsolar point.
Problem (3pts): It is valuable to know what the maximum angle of the Sun will be on a given day at any location. Higher maximum Sun angles are higher energy; conversely, lower maximum Sun angles are lower energy. This angle can be calculated for any location by first calculating the total difference (in degrees) between the latitude of your chosen location and the subsolar point for that day and then subtracting this number from 90º (i.e. Max Sun Angle = 90 – Latitudinal Distance). Calculate the maximum angle of the Sun in L.A. on the following dates:
Latitude of Latitude of the Latitudinal Maximum Sun Los Angeles Subsolar point Difference* Angle
A. June Solstice 34º North
B. September 34º North Equinox
C. December Solstice 34º North
D. March Equinox 34º North
• This difference is in degrees but it’s an angular distance not a latitude! Be sure to calculate this difference from your position north or south of the equator as appropriate.
Questions: Circle the correct answer(s) 8. The two most important things which determine the amount of energy falling on a location in one day are: (Remember to circle two answers here) a. the changing strength of solar rays b. the angle of the Sun upon the surface (angle of incidence or “solar altitude”) c. cloud cover d. the duration of daylight e. that location’s height above sea level
9. The angle of the Sun above the horizon at noon time: a. changes 47º from Solstice to Solstice b. changes 47º from Solstice to Equinox c. is the way to measure longitude d. stays the same throughout the year e. is the lowest the sun will be that day
10. The seasons are caused by: a. the shape of the elliptical orbit of the Earth around the Sun b. the tilt of the axis of the Earth with respect to the plane of the ecliptic c. the orbit of the moon around the Sun d. changes in the energy output of the Sun itself e. none of these
11. The Earth’s ______causes some parts of its surface to receive less solar radiation than others. a. magnetism b. rotation c. curvature d. elliptical orbit e. gravity
12. The axis of the Earth points to the North Star (“Polaris”) all year. a. True b. False
13. On September 22, the noon Sun is directly overhead at the: a. Equator b. Tropic of Cancer c. Tropic of Capricorn d. Plane of the Ecliptic e. Prime Meridian
14. There are always 12 hours of daylight and 12 hours of darkness at the poles. a. True b. False
15. Solar altitude & the duration of daylight work together to increase differences between summer & winter. a. True b. False
16. Summer and winter are reversed in time between the Southern and Northern hemispheres. a. True b. False
Match the following labels to the letters on the diagram below:
17. Earth’s axis ______18. Angle of tilt of the Earth’s axis ______19. Circle of Illumination ______20. Tropic of Capricorn ______21. Antarctic Circle ______22. “Subsolar point” on March 20 and September 22 ______23. “Subsolar point” on Dec 21 (where most direct rays of the Sun hit that day) ______24. “Subsolar point” on June 21 (where most direct rays of the Sun hit that day) ______