Solar System & Earth Exercise Solutions | KalviGavani

How to Use This Page

This page provides complete exercise solutions for Chapter 2 — The Solar System and the Earth from the Samacheer Kalvi Class 11 Geography textbook. Every section of the exercise is answered: MCQs, fill-in-the-blanks, true or false, match the following, short answers, and detailed long answers.

Recommended approach:

1. Read the Key Concepts section first for a quick recap of all important topics. 2. Attempt each exercise section on your own before reading the answers. 3. Compare your answers with the solutions provided here. 4. Use the Common Mistakes to Avoid and Exam Checklist sections before your exam to catch frequent errors.

All answers follow the TN State Board marking scheme — brief answers carry roughly 2 marks, detailed answers carry 5 marks.

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Key Concepts (Quick Recap)

The Solar System

The solar system consists of the Sun and all celestial objects bound by its gravity — eight planets, their moons, dwarf planets, asteroids, comets, and meteoroids. The Sun contains 99.86% of the total mass of the solar system.

Components of the solar system:

Inner (Terrestrial) vs Outer (Jovian) Planets

Earth's Rotation

Rotation is the spinning of the Earth on its imaginary axis from west to east.

Effects of rotation:

1. Day and night — the most direct effect; the hemisphere facing the Sun experiences day, the opposite hemisphere experiences night. 2. Tides — the gravitational pull of the Moon and Sun causes tidal bulges; Earth's rotation carries locations through these bulges. 3. Coriolis effect — moving objects are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere; influences wind patterns and ocean currents. 4. Shape of the Earth — rotation causes the equatorial bulge, making Earth an oblate spheroid (slightly flattened at the poles). 5. Daily temperature variation — rotation alternates heating and cooling cycles.

Earth's Revolution

Revolution is the movement of the Earth around the Sun in an elliptical orbit.

Effects of revolution:

1. Seasons — caused by the combined effect of axial tilt and revolution. 2. Varying length of day and night — as Earth revolves, different latitudes receive varying durations of sunlight. 3. Changes in the altitude of the Sun — the Sun appears higher or lower in the sky depending on the season and latitude. 4. Perihelion and aphelion — Earth is closest to the Sun around January 3 (perihelion, ~147 million km) and farthest around July 4 (aphelion, ~152 million km).

Earth's Axial Tilt (23.5°)

The Earth's axis is inclined at 23.5° to the plane of the ecliptic (the orbital plane). This tilt is the primary reason for:

• The change of seasons throughout the year.
• The shift of the Sun's vertical rays between the Tropic of Cancer (23.5°N) and the Tropic of Capricorn (23.5°S).
• The existence of the Arctic and Antarctic Circles at 66.5°N and 66.5°S respectively.

If the axis were not tilted (0°), there would be no seasonal variation — the equator would always receive direct sunlight, and the poles would always be in twilight.

Solstices and Equinoxes

Latitude and Longitude

Latitude (parallels): Imaginary circles running east-west, parallel to the Equator. They measure distance north or south of the Equator (0° to 90°).

Longitude (meridians): Imaginary semi-circles running from pole to pole. They measure distance east or west of the Prime Meridian (0° to 180°).

Important parallels of latitude:

Important meridians:

Time Zones, IST, and the International Date Line

• Earth rotates 360° in 24 hours, so 1 hour = 15° of longitude and 1° = 4 minutes.
• The world is divided into 24 standard time zones, each roughly 15° wide.
• Indian Standard Time (IST): UTC + 5:30, based on the 82.5°E meridian passing through Mirzapur (Uttar Pradesh). India uses a single time zone.
• International Date Line: Located at approximately 180° longitude. Crossing it westward adds a day; crossing it eastward subtracts a day. It zigzags to avoid splitting countries or island groups.

Eclipses

Solar Eclipse: Occurs when the Moon comes between the Sun and the Earth, casting a shadow on Earth. Types:

• Total solar eclipse — the Moon completely blocks the Sun.
• Partial solar eclipse — the Moon blocks only part of the Sun.
• Annular solar eclipse — the Moon is farther away, leaving a ring (annulus) of the Sun visible.

Lunar Eclipse: Occurs when the Earth comes between the Sun and the Moon, and Earth's shadow falls on the Moon. Types:

• Total lunar eclipse — the Moon passes through the umbra (dark shadow) of Earth.
• Partial lunar eclipse — only part of the Moon enters the umbra.

Eclipses occur only during a new moon (solar eclipse) or a full moon (lunar eclipse), and only when the Moon's orbit is aligned with the ecliptic plane.

Perihelion and Aphelion

Note: Seasons are NOT caused by the distance variation between perihelion and aphelion. Earth is actually closer to the Sun during the Northern Hemisphere winter. Seasons are caused by axial tilt.

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I. Choose the Best Answer (MCQs)

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II. Fill in the Blanks

1. The Earth rotates from west to east.

2. The imaginary line joining the North Pole and the South Pole is called the axis.

3. The Sun is directly overhead the Equator on March 21 and September 23 (equinoxes).

4. The angle of inclination of the Earth's axis to the orbital plane is 23.5°.

5. The planet nearest to the Earth is Venus.

6. The longest day in the Southern Hemisphere occurs on December 22.

7. The Indian Standard Time is based on 82.5°E longitude.

8. The Earth completes one revolution around the Sun in approximately 365.25 days.

9. The circle of illumination divides the Earth into the day and night hemispheres.

10. When the Moon comes between the Sun and the Earth, it causes a solar eclipse.

11. The Tropic of Cancer is located at 23.5°N latitude.

12. The difference in time between two places 15° of longitude apart is 1 hour.

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III. True or False

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IV. Match the Following

Completed matches:

1. Summer Solstice (NH) — June 21 (c) 2. Winter Solstice (NH) — December 22 (d) 3. Vernal Equinox — March 21 (a) 4. Autumnal Equinox — September 23 (e) 5. Perihelion — January 3 (f) 6. Aphelion — July 4 (b)

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V. Answer Briefly

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VI. Answer in Detail

Effects of Rotation

1. Day and night: As the Earth rotates from west to east, the hemisphere facing the Sun experiences day while the opposite hemisphere experiences night. One complete rotation gives one cycle of day and night (approximately 24 hours).

2. Tides: The gravitational pull of the Moon and the Sun, combined with Earth's rotation, produces two high tides and two low tides roughly every 24 hours and 50 minutes. Rotation carries coastal locations through the tidal bulge.

3. Coriolis effect: Because the Earth rotates, freely moving objects (winds, ocean currents, aircraft, projectiles) are deflected — to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This shapes global wind belts and cyclonic systems.

4. Shape of the Earth: Continuous rotation creates a centrifugal force that is greatest at the equator, causing the equatorial bulge. This makes the Earth an oblate spheroid — the equatorial diameter (12,756 km) exceeds the polar diameter (12,713 km) by about 43 km.

5. Daily temperature cycle: Rotation alternates heating (day) and cooling (night), producing diurnal temperature variations.

6. Time determination: The 360° rotation in 24 hours means every 1° of longitude equals 4 minutes of time difference, forming the basis of time zones worldwide.

Effects of Revolution

1. Seasons: The tilt of Earth's axis (23.5°) means different hemispheres receive varying amounts of solar energy as Earth orbits the Sun. When the Northern Hemisphere tilts toward the Sun, it experiences summer; when it tilts away, it experiences winter. The Southern Hemisphere has the opposite season.

2. Varying length of day and night: During summer in a hemisphere, days are longer than nights; during winter, nights are longer. At the equinoxes, day and night are equal everywhere.

3. Altitude of the Sun: The Sun appears higher in the sky during summer and lower during winter. The noon Sun is directly overhead at the Tropic of Cancer on June 21 and at the Tropic of Capricorn on December 22.

4. Perihelion and aphelion: The elliptical orbit means Earth's distance from the Sun varies — closest on January 3 (perihelion, ~147 million km) and farthest on July 4 (aphelion, ~152 million km). However, this distance variation does NOT cause seasons.

5. Shift of the overhead Sun: Over the course of a year, the vertical rays of the Sun migrate between 23.5°N and 23.5°S, defining the tropics and driving seasonal weather patterns in the tropical and temperate zones.

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1. Equator (0°)

The Equator is the longest parallel of latitude, running midway between the North Pole and the South Pole. It divides the Earth into two equal halves — the Northern Hemisphere and the Southern Hemisphere. At the Equator, day and night are always approximately equal (12 hours each). The Equator receives the maximum vertical rays of the Sun throughout the year, making it the warmest region on Earth.

2. Tropic of Cancer (23.5°N)

This parallel marks the northernmost latitude where the Sun can be directly overhead. This occurs on June 21 (summer solstice in the Northern Hemisphere). On this date, all locations north of the Tropic of Cancer experience their longest day of the year. The Tropic of Cancer passes through India (near Vidisha, Madhya Pradesh), Mexico, Egypt, Saudi Arabia, and other countries.

3. Tropic of Capricorn (23.5°S)

This is the southernmost latitude where the Sun can be directly overhead. This occurs on December 22 (summer solstice in the Southern Hemisphere). On this date, all locations south of the Tropic of Capricorn experience their longest day. The Tropic of Capricorn passes through Australia, Brazil, Namibia, and other countries.

4. Arctic Circle (66.5°N)

This parallel marks the southern limit of the midnight Sun in the Northern Hemisphere. North of the Arctic Circle, the Sun does not set on the summer solstice (June 21) and does not rise on the winter solstice (December 22). The region experiences 24 hours of daylight in summer and 24 hours of darkness in winter at the pole.

5. Antarctic Circle (66.5°S)

This parallel marks the northern limit of the midnight Sun in the Southern Hemisphere. South of the Antarctic Circle, the Sun does not set on December 22 and does not rise on June 21. The phenomena here are the reverse of those in the Arctic region.

Significance of these parallels

• They define the major climatic zones of the Earth: Torrid Zone (between the Tropics), Temperate Zones (between Tropics and Circles), and Frigid Zones (beyond the Circles).
• They determine the position of the overhead Sun and the resulting seasonal changes.
• They influence agricultural patterns, biodiversity distribution, and human settlement zones across the planet.
• The numerical values (23.5° and 66.5°) are directly derived from Earth's 23.5° axial tilt, connecting the parallels to the fundamental cause of seasons.

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Solstices

A solstice occurs when the Sun reaches its greatest declination (angular distance) north or south of the celestial equator. There are two solstices in a year:

Summer Solstice (June 21)

• The Northern Hemisphere is tilted maximally toward the Sun.
• The Sun's vertical rays fall directly on the Tropic of Cancer (23.5°N).
• This is the longest day and shortest night in the Northern Hemisphere.
• Locations north of the Arctic Circle (66.5°N) experience 24 hours of daylight (midnight Sun).
• The Southern Hemisphere experiences the shortest day and longest night (winter solstice there).

Diagram description: Imagine the Earth tilted with the North Pole leaning toward the Sun. The Tropic of Cancer is the latitude where sunlight hits directly from above. The area above the Arctic Circle is fully illuminated — even at midnight, the Sun does not set. The area below the Antarctic Circle is in complete darkness.

Winter Solstice (December 22)

• The Northern Hemisphere is tilted maximally away from the Sun.
• The Sun's vertical rays fall directly on the Tropic of Capricorn (23.5°S).
• This is the shortest day and longest night in the Northern Hemisphere.
• Locations north of the Arctic Circle experience 24 hours of darkness.
• The Southern Hemisphere experiences its longest day and shortest night (summer solstice there).

Diagram description: The Earth is shown tilted with the North Pole leaning away from the Sun. The Tropic of Capricorn receives direct overhead sunlight. The Antarctic region is fully illuminated, while the Arctic region is in prolonged darkness.

Equinoxes

An equinox occurs when the Sun is directly above the Equator, and day and night are of approximately equal duration (12 hours each) everywhere on Earth.

Vernal (Spring) Equinox — March 21

• The Sun is directly overhead the Equator (0°).
• Day and night are equal (12 hours each) across the globe.
• Marks the beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere.
• The Sun appears to move northward after this date.

Autumnal Equinox — September 23

• The Sun is again directly overhead the Equator (0°).
• Day and night are equal (12 hours each) across the globe.
• Marks the beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere.
• The Sun appears to move southward after this date.

Diagram description for equinox: The Earth is shown with its axis tilted but the Sun's rays hitting the Equator directly. The circle of illumination passes through both poles, dividing every latitude exactly in half — one half in daylight, one half in darkness. This symmetry shows why day and night are equal everywhere.

Summary Table

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Common Mistakes to Avoid

1. Confusing rotation with revolution. Rotation = spinning on axis (causes day/night). Revolution = orbiting the Sun (causes seasons). Do not mix these up.

2. Saying seasons are caused by Earth's distance from the Sun. Seasons are caused by axial tilt (23.5°), not distance. Earth is actually closer to the Sun in January (perihelion) — during Northern Hemisphere winter.

3. Writing "23° or 23½°" inconsistently. Always write the axial tilt as 23.5° (or 23½°) — do not round it to 23°.

4. Confusing perihelion/aphelion with perigee/apogee. Perihelion and aphelion refer to Earth's distance from the Sun. Perigee and apogee refer to the Moon's distance from Earth.

5. Mixing up solstice dates and hemispheres. June 21 = summer solstice for the Northern Hemisphere but winter solstice for the Southern Hemisphere. Always specify which hemisphere you are referring to.

6. Saying equinoxes mean "exactly" 12 hours of day. Equinox literally means "equal night," and day and night are approximately equal. Due to atmospheric refraction and the definition of sunrise/sunset, daytime is actually slightly longer than 12 hours on the equinox.

7. Forgetting that the International Date Line is not a straight line. It zigzags to accommodate political boundaries. Do not describe it as a perfect 180° meridian.

8. Confusing the circle of illumination with the axis. The circle of illumination is the line separating day and night. It is perpendicular to the Sun's rays, not aligned with the axis. The axis is tilted at 23.5° to the perpendicular of the orbital plane.

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Exam Checklist

Before your exam, make sure you can confidently answer the following:

• [ ] Define rotation and revolution and list at least 3 effects of each.
• [ ] State the angle of the Earth's axial tilt and explain its significance for seasons.
• [ ] Name all 5 important parallels of latitude with their degree values and significance.
• [ ] Explain the 4 key dates: summer solstice (June 21), winter solstice (December 22), vernal equinox (March 21), and autumnal equinox (September 23).
• [ ] Describe where the Sun is directly overhead on each solstice and equinox.
• [ ] Define perihelion and aphelion with their approximate dates and distances.
• [ ] Explain solar and lunar eclipses and why they do not occur every month.
• [ ] Calculate time differences using longitude (1° = 4 minutes, 15° = 1 hour).
• [ ] Explain the Coriolis effect and its influence on winds and ocean currents.
• [ ] Distinguish between inner (terrestrial) and outer (Jovian) planets with at least 4 differences.

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Related pages on KalviGavani:

• [Class 11 Geography — All Chapter Solutions](/class/11/geography/solutions)
• [Class 11 Geography — The Solar System and the Earth Chapter Guide](/class/11/geography/the-solar-system-and-the-earth)
• [Class 11 TN Board — All Subjects](/class/11/tamil-nadu-state-board)