1. Insolation and Angles

3. Celestial sphere
Zenith
West
Observer
South
North
Horizon
East

4. All sunlight is the same—it comes from the same sun to the same Earth.
But all sunlight does not “hit the Earth” the same way!

5. Solar energy that reaches Earth’s surface
Incoming solar radiation
Insolation
Solar energy that reaches Earth’s surface

6. During which month does the Sun appear to rise the highest in the sky for an observer in New York State?
(1) December (3) June
(2) September (4) March
High in sky = Greater Angle of Insolation
=SUMMERTIME!

7. Angle of Insolation Some light strikes with a low angle,
provides less heat and makes a long shadow.

8. Notice how shadow indicates angle of insolation!
Some light strikes with a great angle,
provides more heat and makes a small shadow.

9. Over the course of the day shadows decrease, then increase again.
As shadows increase the
angle of insolation decreases.

10. Angle of Insolation Which is the smaller angle of insolation?
Which will make a SHORTER shadow?
Which will make the ground hotter?

11. (2) March 21 (4) They are all equal
The diagram shows the apparent daily path of the Sun, as viewed by an observer at a certain latitude on three different days of the year.
Which apparent Sun path provides the observer with the greatest angles of insolation?
(1) Dec 21 (3) June 21
(2) March 21 (4) They are all equal

12. Why is a greater angle hotter?

13. Which light waves are more concentrated?
Which light waves are more diffuse?

14. They are both equal! Which has more energy?
The Sun’s rays are always the same, but some are diffuse and some are concentrated.

15. Which diagram best shows the noon Sun providing an observer with the greatest amount of insolation?
WHY?