Key Idea: As the earth turns, the intensity of the energy from sunlight striking a place rises and falls over the course of a day. The maximum intensity of the energy from sunlight striking a place is greater the closer the place comes to passing directly beneath the sun.

Students are expected to know that:

  1. As the earth rotates on its axis, a place that is in darkness rotates into sunlight, crosses through the sunlit side of the earth, and then rotates back into darkness.
  2. When any given place rotates into sunlight, the sun at that place appears at the eastern horizon, and the sunlight strikes at an angle that is parallel to the surface of the earth (0° angle). As the earth rotates toward the east, the sun gets higher and higher in the sky and the angle at which sunlight strikes the place gets larger and larger. When the place is directly north or south of the place that is directly under the sun, it is the middle of the day at that place and the sun is as high as it will get in the sky (the closest it will get to 90°). As the earth continues to rotate, the sun at that place appears lower and lower in the sky, and the angle that sunlight strikes that place gets smaller and smaller. Finally the place rotates out of sunlight. At sunset, the sun appears at the horizon and sunlight reaches that place at an angle that is parallel to the earth’s surface (0° angle).
  3. As the earth rotates on its axis, the location where the sunlight is striking the surface of the earth at 90° (sub-solar point) is shifted. All places that pass directly beneath the sun during a given day are the same distance from the equator (are at the same latitude), and they all receive higher intensity sunlight over the course of that day than any other place on the surface of the earth.
  4. The farther a place is north or south of the place that passes directly beneath the sun, the lower the intensity of sunlight that place receives over the day.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
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CL085002

The intensity of sunlight at a place on the surface of the earth changes over the course of a day because the height of the sun above the horizon at that place changes over the course of the day.

31%

37%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

CLM064

The intensity of sunlight at a place changes during the day because the distance sunlight travels to reach that place changes throughout the day (AAAS Project 2061, n.d.).

29%

35%

CLM065

The intensity of sunlight at a place changes during the day because the amount of atmosphere sunlight travels through changes throughout the day (AAAS Project 2061, n.d.).

22%

17%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.