# Season and Axis Angle

Topics: Season, Solstice, Equator Pages: 10 (2003 words) Published: February 26, 2014

Student Exploration: Seasons: Why do we have them?

Vocabulary: direct sunlight, Earth’s axis, equator, indirect sunlight, northern hemisphere, North Pole, season, solstice, southern hemisphere, South Pole, summer solstice, winter solstice

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

1. At what time of day is sunlight strongest – in the early morning (when the Sun has just risen) or at noon (when the Sun reaches its highest point)? At noon when the Sun reaches its highest point.

2. At what time of year does the noon Sun rise highest in the sky? During the summer time.

3. Based on your answers, why is it warmer in summer than in winter? It is warmer in the summer then in the winter because the Earth’s tilt is faced towards the Sun.

Gizmo Warm-up
The reasons for seasons have a lot to do with the angle at which the Sun’s rays hit Earth. To see why, select the PLATE tab on the Seasons: Why do we have them? Gizmo™. The image shows a solar panel (Plate M) facing the Sun. Check that the Axis angle is set to 0˚.

1. Click Fire to release 100 “rays” of sunlight. Look next to “Number of hits” below the plate.

How many of these rays hit Plate M? 100

2. Click Reset. Change the Axis angle to 40˚, and click Fire. How many rays hit Plate M now? 76

3. Which do you think will warm up the plate more quickly? (Circle one.)

A. Direct sunlight (sunlight that hits the plate at a 90° angle) B. Indirect sunlight (sunlight that hits the plate at an angle of less than 90°)

Activity A:

Sunlight on a plate
Click Reset.

Question: How does the angle of sunlight affect the amount of energy that is absorbed?

1. Form hypothesis: How do you think the angle of the plate will affect how much sunlight hits the plate? The closer the angle is to zero, the more sunlight that will hit the plate.

2. Collect data: Set the Axis angle to -80° and click Fire. Record the Number of hits. Repeat for each angle and fill in the tables below. You can use the slider or type the number into the text field directly and click Enter on your keyboard. (Note that “0°” appears in both tables.)

Axis angle
Hits
-80°
18
-60°
50
-40°
76
-20°
92

100

Axis angle
Hits

100
20°
92
40°
76
60°
50
80°
18

3. Analyze: What is the relationship between the axis angle and the number of solar rays that hit the plate? The closer the angle is to zero, the more solar rays that hit the plate.

4. Interpret: Select the GRAPH tab. What does the graph show? The graph shows a number dots where the plate angle is measured with the number of hits. Every time I fire sunlight at a certain angle a dot shows up. The negative angled dots have a direct mirror image of them on the positive angled dots. They also have the same number of hits. A negative angle like -80 would have 18 hits compared to a positive angle like 80 with also 18 hits. Both would be a mirror dot of the other on each side of the graph.

5. Apply: At what angle will the plate get the hottest? 0 axis angle ­­
6. Extend your thinking: The plate is a model for how sunlight hits Earth’s surface.

A. Which parts of Earth are most similar to the plate with an axis angle of 0°? Explain. The equator, because that is an investable line that receives the most amount of sunlight like the axis angle of zero. B. Which parts of Earth are most similar to the plate with an axis angle of 80°? The North and South poles because that is where the sunlight hits the least like the axis angle of 80.

Activity B:

Sunlight on Earth
Select the EARTH tab on the left and the DESCRIPTION tab on the right. Check that the Axis angle is set to 0 degrees.

Question: What causes seasons on Earth?

1. Predict: Look at the image of Earth (not to scale). Plate A is located at the North Pole, and plate G is located at the South Pole. Plates D and J are located at the equator.

A. Of the...