Earth, Moon, and the Sun – Class 7 Science notes, important questions and MCQs

Chapter overview

Earth rotates on its axis and revolves around the Sun, while the Moon revolves around Earth. These motions cause day and night, years, phases of the Moon and eclipses.

Motions

• Earth rotates west to east once in about 24 hours → day and night; the Sun appears to rise in the east.
• Earth revolves around the Sun in about 365¼ days → a year.
• The Moon revolves around Earth in about 27 days; we always see the same side of the Moon.

Phases and eclipses

• Phases: new moon → waxing crescent → first quarter → full moon → waning → new moon (about 29.5 days).
• Lunar eclipse: Earth's shadow falls on the Moon (only on a full moon night).
• Solar eclipse: Moon's shadow falls on Earth (only on a new moon day); never look at the Sun directly.

Key terms

Axis

imaginary line around which Earth rotates

Phases of the Moon

different shapes of the bright part of the Moon seen from Earth

Eclipse

blocking of light of one body by another

Formulas

• Rotation ≈ 24 h; revolution ≈ 365¼ days

Important questions with answers

Quick revision

• Rotation → day and night.
• Revolution → year.
• Same face of the Moon always faces Earth.

Exam tips

• Lunar eclipse = full moon; solar eclipse = new moon.
• The Moon shines by reflected sunlight.

Practice MCQs

1. Day and night happen because Earth

   1. revolves
   2. has a moon
   3. is round only
   4. rotates
   Show answer

   Answer: (d) rotates. Rotation.

2. The Sun appears to rise in the

   1. east
   2. west
   3. north
   4. south
   Show answer

   Answer: (a) east. Earth rotates west to east.

3. A lunar eclipse can happen only on a

   1. new moon
   2. any day
   3. half moon
   4. full moon
   Show answer

   Answer: (d) full moon. Earth between Sun and Moon.

4. The time between two full moons is about

   1. 7 days
   2. 15 days
   3. 29.5 days
   4. 365 days
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   Answer: (c) 29.5 days. Lunar month.

5. Day and night are caused by the Earth's

   1. revolution
   2. distance from Moon
   3. tilt only
   4. rotation
   Show answer

   Answer: (d) rotation. Spinning on its axis.

6. We always see the same side of the Moon because

   1. the Moon does not rotate
   2. the far side is dark always
   3. Earth blocks the other side
   4. its rotation and revolution take the same time
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   Answer: (d) its rotation and revolution take the same time. Synchronous rotation.

7. Why should we not look at a solar eclipse with naked eyes?

   1. it is unlucky
   2. the Moon is harmful
   3. strong sunlight can damage the eyes
   4. it causes eclipses
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   Answer: (c) strong sunlight can damage the eyes. Use safe solar filters.

8. A solar eclipse occurs when

   1. the Moon comes between Sun and Earth
   2. Earth comes between Sun and Moon
   3. the Sun comes between Earth and Moon
   4. Moon is full
   Show answer

   Answer: (a) the Moon comes between Sun and Earth. Moon's shadow falls on Earth.