Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which phase occurs when the moon is half illuminated and expanding?

1. Waning gibbous

2. First quarter

3. Waxing crescent

4. New moon

The correct answer is: First quarter

The phase when the moon is half illuminated and expanding is known as the First Quarter. During this phase, one half of the moon is illuminated by the Sun, while the other half is in shadow. The term "waxing" indicates that the illuminated portion is increasing, leading up to the Full Moon phase. In the context of the moon's cycle, the First Quarter occurs approximately one week after the New Moon. At this point, the moon is positioned at a right angle with respect to the Earth and the Sun, allowing us to see it as a semi-circle in the sky. This phase represents a critical point where observers can begin to notice the growth of the moon's illuminated surface, contrasting sharply with the darkness of the New Moon where the moon is not visible from Earth. Understanding the terminology associated with the lunar phases is essential, as it helps clarify the moon's position relative to Earth and the Sun throughout its cycle.