Theory question 202
The Earth and Solar System(a) Highlight any three effects of either rotation or revolution of the earth
(b) Give reasons why: (i) all areas north of the Arctic Circle have twenty four hours of daylight on June 21 (ii) areas within the tropics have more sunshine than areas outside the tropics
Show the model answer
(a) Rotation: day and night; deflection of winds and ocean currents (Ferrel's law/Coriolis); time difference of 4 minutes per degree of longitude; rising and falling of tides; sunrise in the east and sunset in the west. (Revolution: seasons, varying length of day and night, changing altitude of the midday sun)
(b)(i) The earth's axis is tilted 23½° and on 21 June the North Pole is tilted towards the sun; the sun is overhead at the Tropic of Cancer and its rays reach 23½° beyond the North Pole, so the whole area north of 66½°N stays in sunlight throughout the earth's rotation
(ii) The midday sun is always high and is overhead twice a year within the tropics, so rays are concentrated; day length is about 12 hours all year with no long winter nights; rays pass through less atmosphere
Use the tilt of the axis in (b).