Which moon phase is characterized by the right half of the Moon being illuminated?

Which moon phase is characterized by the right half of the Moon being illuminated?

• A. First Quarter
• B. Full Moon
• C. Third Quarter
• D. New Moon

Answer: (A)

The phase you’re describing comes from how the Sun lights the Moon as it orbits Earth. When the Moon is about a week past the new Moon, we see exactly half of its near side lit—the right half in the Northern Hemisphere—while the other half is in shadow. The line dividing day and night on the Moon (the terminator) runs roughly top-to-bottom, making the right side appear bright. This is the first quarter. Note that in the Southern Hemisphere the illuminated half would appear on the left, due to the different viewing perspective. By contrast, a Full Moon shows the entire disk lit, a New Moon shows none lit, and the Third Quarter shows the left half lit.

The phase you’re describing comes from how the Sun lights the Moon as it orbits Earth. When the Moon is about a week past the new Moon, we see exactly half of its near side lit—the right half in the Northern Hemisphere—while the other half is in shadow. The line dividing day and night on the Moon (the terminator) runs roughly top-to-bottom, making the right side appear bright. This is the first quarter.

Note that in the Southern Hemisphere the illuminated half would appear on the left, due to the different viewing perspective. By contrast, a Full Moon shows the entire disk lit, a New Moon shows none lit, and the Third Quarter shows the left half lit.