The Sun's rays and climate demonstration allows students to visualize how the incoming angle of the Sun’s rays affects the concentration of solar energy on areas of the Earth. This demonstration should take approximately 10 minutes.

 

Important: Review all procedures in The Sun’s Rays and Climate Demonstration handout prior to implementing this demonstration. The Sun's Rays and Climate Demonstration handout contains background information, a list of required materials, demonstration procedures, and discussion questions.

 

The amount of energy coming from the Sun is nearly constant. However, since the Earth’s shape is spherical, the Sun’s rays strike the Earth’s surface at different angles, creating variances in temperatures on Earth. The equator receives the most direct sunlight because sunlight arrives at a perpendicular (90 degree) angle to the Earth. Sunlight rays are concentrated on smaller surface areas, causing warmer temperatures and climates. As incoming rays move further away from the equator, solar intensity decreases. This is due to decreasing incoming sunlight angles that result in the sun’s rays being spread out over a greater surface area of the Earth. Latitudes near the poles always receive the Sun’s rays at lower angles, thus creating a colder climate. In the middle latitudes, the angle of the Sun’s incoming rays varies from lower in the winter to higher in the summer, causing seasonal temperature changes.

 

1. Position the flashlight pointing straight down at the graph paper at a 90-degree angle. Hold the flash light about 15 cm above the graph paper. Ask a student to draw a line around the outer edge of the light circle that is projected on the paper. Ask another student to count the number of squares that are lit. If a square is more than 1/2 lighted it counts as one square. Instruct the student to record the number of squares.

 

2. Position the flashlight pointing straight down at the graph paper at a 45-degree angle. Hold the flash light about 15 cm above the graph paper. Ask a student to draw a line around the outer edge of light circle that is projected on the paper. Ask another student to count the number of squares that are lit. If a square is more than 1/2 lighted it counts as one square. Instruct the student to record the number of squares.

 

3. Have students discuss how the area of the light on the graph paper changes with different incoming angles. Discuss the results with students. See the Sun’s Rays and Climate Demonstration handout for discussion questions. Ask students to explain how the angle of incoming rays of the Sun can affect the Earth's climate? Clarify any concepts as needed.

 

4. Show the video clip: How does the Sun's energy get into the climate system?

 

Note: The video clip is a large file. You may wish to download the video clip to your computer prior to using it in your classroom.

 

5. Instruct students to complete their Planetary Energy Balance Exploration Sheet from yesterday's lesson.

 

6. Ask students to go to the Student Resources Web page and click the Planetary Energy Balance link. Instruct students to read the content pages about planetary energy balance and answer the questions on their exploration sheets.

 

7. Review students' responses to the questions and explain and clarify terminology and concepts as needed.