1. Earth, sun and moon

2. Intensity is decreased as angle changes
Intensity = max
Intensity is decreased as angle changes
Angle = 90
Angle = 0
Intensity = 0

3. Direction of rotation
North Pole
Sun’s rays
Axis
DAY
NIGHT

4. A year is the time for the Earth to orbit the Sun.
1 Earth year = days
Sept
SUN
June
Dec
Direction of orbit
A year is the time for the Earth to orbit the Sun.
March

5. The sun’s rays are pretty close to parallel when they reach the surface of the Earth.
Earth’s axis
Equator
If the Earth’s axis was always perpendicular to the Sun’s rays then direct sunlight would always shine on the equator and we would have no seasons. S

6. However, the Earth actually exists so where its angle of rotation is at an angle of 23.5O to its plane of orbit N
Angle of incidence
= 23.5O
Earth’s axis
Plane of orbit
Equator S

7. The Earth maintains this angle throughout its entire orbit.

8. Source: http://daphne. palomar. edu/jthorngren/tutorial
Source: accessed 15th August, 2007

9. Source: http://daphne. palomar. edu/jthorngren/tutorial
Source: accessed 15th August, 2007

10. Animation of Phases of Moon
Source: accessed 16th August, 2007
Animation of Phases of Moon