What type of moon occurs when one week after the semi-circular moon appears, almost one-half of the moon is visible?

The timing of the lunar phases is crucial to understanding this question. One week after a semi-circular moon, which is the first quarter moon, indicates that the moon has moved to a phase where approximately half of its surface is illuminated. This phase is often referred to as the "half moon" or "first quarter," and is characterized by exactly half of the moon being visible from Earth. It occurs approximately a week after the new moon when the moon is not visible at all and then progresses to the first quarter where the right half is illuminated in the Northern Hemisphere.

In contrast, other phases such as the full moon and crescent moon represent different percentages of illuminated moon and occur at different times in the lunar cycle, making them incorrect in this context. The new moon phase, occurring before the first quarter, also indicates little to no illumination, ruling it out as well. Therefore, the description provided aligns perfectly with the characteristics of the first quarter moon.