Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The Moon is Earth's only natural satellite. It is a non-luminous body, meaning it does not produce its own light; it reflects light from the Sun.
The changing shapes of the visible bright part of the Moon as seen from the Earth are called the Phases of the Moon.
The sequence of phases depends on the relative positions of the Sun, Moon, and Earth. One complete cycle of phases takes approximately days.
New Moon (Amavasya): This occurs when the Moon is positioned between the Earth and the Sun. The side facing Earth is dark.
Full Moon (Purnima): This occurs when the Earth is between the Sun and the Moon. The entire side facing Earth is illuminated.
Waxing: The period during which the illuminated portion of the Moon visible from Earth increases (from New Moon to Full Moon).
Waning: The period during which the illuminated portion decreases (from Full Moon to New Moon).
Gibbous Moon: When the visible illuminated part is greater than a semi-circle but less than a full circle.
Crescent Moon: When the visible illuminated part is less than a semi-circle.
📐Formulae
💡Examples
Problem 1:
If a Full Moon is observed on the of October, on which approximate date will the New Moon occur in the same month?
Solution:
The New Moon will occur approximately on October or .
Explanation:
The time interval between a Full Moon and the subsequent New Moon is roughly half of the total lunar cycle. Since the total cycle is days, the half-cycle is days. Adding days to the gives the .
Problem 2:
Why do we always see the same side of the Moon from Earth?
Solution:
This is due to Synchronous Rotation.
Explanation:
The Moon takes the same amount of time to complete one rotation on its axis as it takes to complete one revolution around the Earth, which is approximately days. Because these two periods are equal (), the same hemisphere always faces the Earth.