Which phase shows the Moon's left half illuminated in the Northern Hemisphere?

Which phase shows the Moon's left half illuminated in the Northern Hemisphere?

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

Answer: (B)

Think about where the sunlight is coming from and what part of the Moon we can see from Earth. The illuminated portion is the part facing the Sun, and when the Moon is about 90 degrees away from the Sun in the sky, we see half of its near side lit. In the Northern Hemisphere, that half-illuminated view corresponds to the last (third) quarter of the Moon’s cycle. At this phase, the left half of the Moon’s near side is illuminated while the right half is dark. This phase happens roughly a week after the Full Moon and about a week before the New Moon, and you’ll typically notice it in the morning sky as it rises around midnight and is up around sunrise. Other phases show different orientations: the right half is lit at the first quarter, the entire face is lit at Full Moon, and the Moon is almost invisible at New Moon. The key idea is that which half you see lit depends on the Moon’s position relative to the Sun and where you’re standing on Earth.

Think about where the sunlight is coming from and what part of the Moon we can see from Earth. The illuminated portion is the part facing the Sun, and when the Moon is about 90 degrees away from the Sun in the sky, we see half of its near side lit.

In the Northern Hemisphere, that half-illuminated view corresponds to the last (third) quarter of the Moon’s cycle. At this phase, the left half of the Moon’s near side is illuminated while the right half is dark. This phase happens roughly a week after the Full Moon and about a week before the New Moon, and you’ll typically notice it in the morning sky as it rises around midnight and is up around sunrise.

Other phases show different orientations: the right half is lit at the first quarter, the entire face is lit at Full Moon, and the Moon is almost invisible at New Moon. The key idea is that which half you see lit depends on the Moon’s position relative to the Sun and where you’re standing on Earth.