Selina Concise Solutions for ICSE Class 9 Geography Chapter 3 Rotation and Revolution

Exercises

I. Short Answer Questions.

Question 1. What is meant by the earth’s axis ?
Answer: The earth’s axis is the imaginary line joining the North Pole to South Pole, around which the earth rotates.
In simple words: Imagine a long needle passing through the center of a spinning orange from top to bottom. That needle is the axis, the invisible line that Earth spins around.

📝 Teacher's Note: Use a globe and a knitting needle to demonstrate this. Emphasize that the axis is not perfectly upright but tilted at an angle of \( 23.5^{\circ} \).

🎯 Exam Tip: Always mention the two endpoints of the axis—the North Pole and the South Pole—to get full marks.

Question 2. Name the two chief motions of the earth.
Answer: Two chief motions of the earth are rotation and revolution.
In simple words: Earth moves in two ways at once: it spins like a top (rotation) and travels in a big circle around the Sun (revolution).

📝 Teacher's Note: Use the analogy of a spinning dancer moving across a stage to explain how both motions happen simultaneously.

🎯 Exam Tip: Don't confuse the two! Rotation causes day and night, while revolution causes seasons.

Question 3. Describe two characteristics of rotation.
Answer: Two characteristics of rotation are the complete rotation of the earth from west to east in 24 hours and along its tilted axis which is always in the same direction towards the Pole Star.
In simple words: Earth always spins toward the East, taking exactly one day for a full turn, and its top point always aims toward the North Star.

📝 Teacher's Note: Remind students that because we spin West to East, the Sun appears to rise in the East. It is an "apparent" motion.

🎯 Exam Tip: Mention the direction (West to East) and the time (24 hours) as the primary characteristics.

Question 4. Mention two effects of the rotation of the earth.
Answer: Day and night are caused by the rotation and the creation of centrifugal force resulting in a bulge in the equatorial part and flattened top at the poles.
In simple words: Spinning makes half the world face the sun (day) while the other half is dark (night). It also acts like a salad spinner, pushing the Earth's middle out slightly to make it wider.

📝 Teacher's Note: Explain the "Equatorial Bulge" by showing how a spinning ball of soft clay would flatten at the top and bottom.

🎯 Exam Tip: "Day and night" is the most common answer, but mentioning "centrifugal force" or "Coriolis effect" shows higher understanding.

Question 5. Mention any two possible consequences if the axis of the earth was vertical instead of inclined.
Answer:
1. Then at all places on the earth, lengths of day and night would have been equal, i.e. 12 hr of day and 12 hr of night
2. There would have been no seasons.
In simple words: If Earth stood straight up, every single day would be exactly 12 hours long everywhere, and the weather would stay the same all year round—no more summer or winter!

📝 Teacher's Note: This is a "what-if" scenario. Help students visualize that the tilt is what makes the Sun's rays hit different parts of the Earth more directly at different times of the year.

🎯 Exam Tip: The two key points are "equal day/night duration" and "absence of seasonal changes."

Question 6. State one reason why we do not feel the motions of the earth.
Answer: According to the gravitational force every thing is attached to the earth, keeping everything at rest at their original position, unless any external force compels to motivate it.
In simple words: We don't feel the spin because everything around us—the air, the trees, and the ground—is moving along with us at the exact same steady speed, held down by gravity.

📝 Teacher's Note: Compare this to sitting in a very smooth, fast airplane. You don't feel like you are moving hundreds of miles per hour because the cabin is moving with you.

🎯 Exam Tip: Use the term "gravitational force" to explain why we stay attached to the moving Earth.

Question 7. Define ‘revolution’.
Answer: Revolution is the revolving of the earth on its orbit around the sun in 365 days and 6 hours nearly.
In simple words: Revolution is Earth's long journey around the Sun. It takes about a year to finish one full lap.

📝 Teacher's Note: Clarify that the "6 hours" are the reason we have a leap year (Feb 29) every four years (\( 6 \times 4 = 24 \) hours).

🎯 Exam Tip: Always include the approximate time (365 and 1/4 days) in the definition.

Question 8. State two chief characteristics of the revolution of the earth.
Answer: The earth revolves at an average speed of 100,000 km per hour. The earth revolves in an elliptical orbit with two particular positions i.e. perihelion 147.3 million km away from sun in January and aphelion 152 million km away from sun in July.
In simple words: Earth zooms around the Sun extremely fast in an oval shape, not a perfect circle. This means sometimes we are a bit closer to the Sun and sometimes a bit further away.

📝 Teacher's Note: Students often think we are closer to the sun in summer. Correct this by pointing out we are at Perihelion (closest) in January when it's winter in the Northern Hemisphere!

🎯 Exam Tip: Remember: Perihelion = "P" for "Point of Nearness" (January); Aphelion = "A" for "Away" (July).

Question 9. Mention two effects of revolution.
Answer: Two main effects of revolution are the seasonal changes throughout the year and the creation of particular heat zones on temperature zones.
In simple words: Because Earth travels around the Sun, the weather changes from summer to winter, and different parts of the world stay hotter or colder on average.

📝 Teacher's Note: Link this back to the tilted axis. Revolution + Tilt = Seasons. Without either, seasons wouldn't happen.

🎯 Exam Tip: "Seasons" and "Variation in day/night length" are the most standard answers.

Question 10. What is meant by Summer Solstice ? When do we have Summer Solstice in the Northern Hemisphere ?
Answer: Summer Solstice occurs on June 21, in the Northern Hemisphere, when the sun is overhead at the Tropic of Cancer and the North Pole is tilted towards the sun, so the summer season is experienced in the Northern Hemisphere.
In simple words: The Summer Solstice is the "longest day" of the year. It happens in June when the top half of Earth leans closest to the Sun.

📝 Teacher's Note: Mention that while it's the Summer Solstice in the North, it's the Winter Solstice in the South (Australia/South Africa).

🎯 Exam Tip: Be precise with the date (June 21) and the specific line of latitude (Tropic of Cancer).

Question 11. What is meant by Equinox ? Give the dates of the two Equinoxes.
Answer: Equinox means the time when the days and nights are equal all over the world. The particular dates of equinoxes are 21st March (Spring or Vernal Equinox) and 23rd September (Autumnal Equinox).
In simple words: "Equi-nox" means "Equal-night." On these two days, every place on Earth gets exactly 12 hours of light and 12 hours of darkness.

📝 Teacher's Note: The word comes from Latin: *aequus* (equal) and *nox* (night). Use this to help students remember the meaning.

🎯 Exam Tip: Remember both dates: March 21 and September 23.

Question 12. What will be the duration of daylight in the Northern Hemisphere on March 21st at 23°30′ latitude ?
Answer: The duration of daylight will be of 12 hours.
In simple words: Since March 21st is an Equinox, every single place on Earth has 12 hours of daylight, no matter what their latitude is.

📝 Teacher's Note: This is a "trick" question to see if students understand that Equinox means equality *everywhere*.

🎯 Exam Tip: If the date is March 21 or September 23, the answer for day/night length is always 12 hours.

Question 13. What is the relationship of seasons between the Northern and Southern Hemispheres ?
Answer: The seasonal episodes are reciprocal with each other i.e. if Northern Hemisphere experiences summer season, then Southern Hemisphere has winter season; in the same way if . there is spring season in Northern Hemisphere, there is autumn season in Southern Hemisphere and vice-versa.
In simple words: The two halves of the world are seasonal opposites. When we have hot summers, they have cold winters, and when we have blooming spring, they have falling leaves in autumn.

📝 Teacher's Note: This is why Christmas is celebrated in the middle of summer in Australia!

🎯 Exam Tip: Use the word "reciprocal" or "opposite" to describe the relationship.

Question 14. How has the phenomenon of the ‘Midnight Sun’ come about ?
Answer: Beyond the Arctic Circle, the regions experience 24 hours daylight in summer season due to the North Pole facing continuously towards the pole. It is called the ‘Midnight Sun’. Norway is called land of Midnight Sun.
In simple words: At the very top of the world during summer, the Earth's tilt keeps that area facing the Sun even as it spins. This means the Sun never sets, even at midnight.

📝 Teacher's Note: Explain that the Sun appears to circle the sky without ever dropping below the horizon line in these regions.

🎯 Exam Tip: Mention the "Arctic Circle" and "Norway" as they are key geography terms for this concept.

Question 15. What are the seasons in the Northern and the Southern Hemispheres on 23rd September ?
Answer: There are Autumn season and spring season in the Northern and Southern Hemispheres on 23rd September, respectively.
In simple words: On September 23, the North starts getting cooler (Autumn), while the South starts warming up after winter (Spring).

📝 Teacher's Note: This is the Autumnal Equinox for the North and the Vernal Equinox for the South.

🎯 Exam Tip: Always specify which hemisphere has which season; don't just write "Autumn and Spring."

Question 16. Mention one effect of seasons in low and high latitudes.
Answer: The effect of seasons in low and high latitudes is distinct through various phases of different seasons. Low latitude areas get ample temperature and rainfall while the high latitude areas are cold and receive less rainfall. Tropical regions are always warm with heavy rainfall season, while the temperate and polar regions are cold with scanty rainfall, while the polar regions are always covered with perpetual snow due to the temperature below 0°C.
In simple words: Near the middle of the world (low latitudes), seasons bring lots of heat and rain. Near the ends of the world (high latitudes), it stays very cold and dry with snow that never melts.

📝 Teacher's Note: Connect "Low Latitudes" to the "Torrid Zone" and "High Latitudes" to the "Frigid Zone."

🎯 Exam Tip: Use the term "perpetual snow" to describe polar regions and "heavy rainfall" for tropical regions.

II. Give reasons for each of the following

Question 1. We always see the sun rising in the East.
Answer: As the earth moves from West to East, the eastern part gets lighted first and we see the sunrise in the East.
In simple words: Because the Earth spins like a merry-go-round toward the right (East), the Sun comes into view from that direction first.

📝 Teacher's Note: Demonstrate this with a dark room, a globe, and a flashlight. Spin the globe West to East to show the "Sun" appearing over the Eastern horizon.

Question 2. Norway is called the Land of the Midnight Sun.
Answer: Northern part of Norway is beyond the Arctic Circle where the sunlight remains for six months from March to September, so it is called the Land of Midnight sun due to the sunlight seen at night, too.
In simple words: Since Norway is so far North, during the summer half of the year, the Sun is visible 24 hours a day.

Question 3. The speed of the rotation of the earth is greater at the Equator than at the Arctic Circle.
Answer: As every part of the earth takes a frill round within 24 hours, the equator being the largest circle of latitude 0°, the speed is greatest at the equator due to crossing the maximum distance per hour. i.e. it is 1660 km per hour, while it decreases to 0° at poles.
In simple words: Since the middle of the Earth is fatter, a point on the Equator has to travel a much longer distance in the same 24 hours compared to a point near the top, so it has to move much faster.

📝 Teacher's Note: Compare this to two runners on a track. The runner in the outside lane has to run faster to keep up with the runner on the inside lane if they want to finish at the same time.

Question 4. 25 th of December in New Zealand may be one of the hottest days of the year.
Answer: The sun’s rays are vertical over the Tropic of Capricorn, so . 25th December may be one of hottest days in NewZealand, being situated in the Southern Hemisphere.
In simple words: While we have winter in the North in December, it is the peak of summer in the South. New Zealand gets direct, hot sunlight during this time.

Question 5. The length of day and night is not equal at all places on the earth.
Answer: Due to the tilted axis of the’earth and the migration belt of the sun between Tropics of Cancer and. Capricorn, the length of day and night differ from place to place and region to region.
In simple words: Because Earth is tilted, different places spend different amounts of time in the sunlight as the planet spins.

Question 6. The period of twilight and dawn increases polewards.
Answer: On account of the oblique path of the sun towards poles than the vertical path along the equator, the length of dawn and twilight is greater, as it is nearly one hour near equator and 50 days at the poles.
In simple words: Near the middle of Earth, the Sun goes straight down, making it dark quickly. Near the poles, the Sun goes down at a shallow angle, so it stays in the "just about to set" or "just about to rise" zone for a very long time.

Question 7. Noon is hotter than morning.
Answer: Due to the vertical rays of the sun at noon and the slanting rays in the morning, Noon is hotter than morning.
In simple words: At noon, the Sun is directly above you, focusing all its heat on a small spot. In the morning, the light is tilted and spread out, so it feels weaker.

Question 8. Days and nights are equal at all places on earth on March 21.
Answer: The rays of the sun fall vertical on the equator or the middle part of the earth, on March 21, So the distribution of light is equal all over the world resulting the duration of the day and night equal from pole to pole. It is called the Vernal Equinox.
In simple words: On this day, the Sun is perfectly aligned with the Earth's middle, giving everyone exactly half light and half dark.

Question 9. Vertical rays are hotter than slanting rays.
Answer: Vertical rays are hotter, because these cross shorter distance from the sun to the earth. Consequently the tropical belt is hotter than temperate and polar areas.
In simple words: Straight rays don't have to travel through as much air to reach the ground, so they don't lose their heat. They also stay focused in one hot spot instead of spreading out.

Question 10. Though the earth is nearest to sun in winter yet the winter is cool.
Answer: During the Winter Solstice the earth’s Southern pole is facing towards the sun and the Northern Hemisphere experiences winter season and cold inspite of the earth’s nearest position to the sun.
In simple words: Distance doesn't matter as much as tilt! Even though we are closer to the Sun in January, the Northern half of Earth is leaning away from the Sun, which makes it cold.

III. Long Answer Questions

Question 1. What is meant by rotation of the earth ? Discuss the effect of the rotation of the earth.
Answer:
(a) Rotation of the earth takes place around the axis of the earth within 24 hours making one complete round.
(b) The rotation causes day and night alternately; the part of the earth facing the sun experiences day and on the opposite side the dark part experiences night. One night and one day together make a complete solar day.
In simple words: Rotation is Earth's spinning motion. It gives us our 24-hour day and creates the pattern of sunlight and darkness we live by.

📝 Teacher's Note: Emphasize that the Sun doesn't actually "move"—we are the ones moving into and out of its light.

🎯 Exam Tip: Always mention "24 hours" and "day and night" as the definition and primary effect.

Question 2. Describe the two interesting phenomena made by the circle of illumination viz., Solstice and Equinox.
Answer: Circle of illumination is the lighted part of the earth by the sun. On June 21, Northern Hemisphere enjoys the longest day due to the sun’s position overhead at the Tropic of Cancer. It is called Summer Solstice. On the other hand when the sun is overhead on the Tropic of Capricorn, the Southern Hemisphere gets the longest day on December 22, which is known as Winter Solstice. The dates of Equinox are 21st March and 23rd September, when the days and nights are equal all over the world and there are spring and autumn seasons in Northern Hemisphere and autumn and spring in Southern Hemisphere respectively.
In simple words: Solstices are the days of extreme light or dark (longest day or shortest day). Equinoxes are the "middle" days where everyone gets an equal amount of both.

📝 Teacher's Note: The "Circle of Illumination" is the line that separates the day side from the night side of the Earth.

🎯 Exam Tip: Memorize the specific dates: June 21, Dec 22, March 21, Sept 23.

Question 3. What is the effect of the inclined axis of the earth on day and night ?
Answer: The difference in the duration of days and nights all over the earth is on account of the inclined axis of the earth. There is six months day in North Pole in summer season (from April to September) and six months day in South Pole in winter season (from October to March).
In simple words: Because the Earth is tilted, the top or bottom gets "stuck" facing the sun for months at a time, while other places see the day length change as the year goes by.

Question 4.
1. On which two days are the days and nights equal all over the world and why ? What name do you give to these days ?
2. Which is the largest and which is the shortest day in the Northern Hemisphere and why ?
3. On which dates does the sun shine vertically overhead at
(a) Equator,
(b) Tropic of Cancer.
(c) Tropic of Capricorn ?
Answer:
1. On 21st March and 23rd September the days and flights are equal all over and world due to the sun’s rays vertical on the equator. The name is Equinox of this position.
2. The largest day is 21st June and the shortest day is 22nd December in the Northern Hemisphere. This is because on June 21, the North Pole is tilted toward the sun, and on Dec 22, it is tilted away.
3. The sun is overhead on :
(a) Equator on 21st March and 23rd September.
(b) Tropic of Cancer on 21st June.
(c) Tropic of Capricorn oh 22nd December.
In simple words: This is a summary of the Sun's "migration" throughout the year. It hits the middle on Equinoxes and the top/bottom boundaries on Solstices.

Question 5. Describe how the duration of sunlight changes from the Equator to the Poles with respect to the angle of incidence.
Answer: As the angle of incidence changes from 0° to 90° from Poles towards the Equator; So the duration of sunlight also changes. Duration of daylight is 12 hours on equator and 24 hours on the North Pole in summer and 24 hours on the South Pole in winter. So the duration of sunlight increases from the Equator to the North Pole and decrease in the winter season and vice-versa in between Equator and South Pole.
In simple words: Near the Equator, you always get about 12 hours of Sun. But as you move toward the poles, the tilt makes the days get much longer in summer (up to 24 hours) and much shorter in winter.

Question 6. With the help of a diagram describe the heat zones.
Answer:
The Earth is divided into three heat zones: 1. Torrid Zone (between the Tropics, very hot), 2. Temperate Zones (moderate weather), and 3. Frigid Zones (near the poles, very cold).
In simple words: The Earth has a "hot belt" in the middle, "mild belts" in the mid-sections, and "ice caps" at the ends.

📝 Teacher's Note: Explain that "Torrid" means burning/parched, "Temperate" means moderate, and "Frigid" means frozen.

🎯 Exam Tip: Drawing this diagram with correct latitude labels (\( 23.5^{\circ} \), \( 66.5^{\circ} \)) is worth many marks.

Question 7. Explain with the help of diagram how the tilt of the earth’s axis and the revolution cause
1. seasons.
2. variation in the length of day and night; and
3. changes in the altitude of the midday sun at different times of the year.
Answer:
1. On account of the different positions of the earth with respect to the sun, in its orbit, various types of seasons are caused. The sun remains vertical on Tropic of Cancer on 21st June and on Tropic of Capricorn on 22nd December and on equator on 21st March and 23rd September.
2. The length of day decreases from the equator to the Poles. Apart from this the polar areas experience six month days and six months nights respectively.
3. The belt of sun’s migration lies between the Tropic of Cancer and Capricorn, consequently the sun remains overhead in this belt, while beyond this belt the sun never remains vertical at noon and the sun’s track remains slanting with shorter curved path in other regions.

In simple words: As Earth travels its oval path, its tilt means first the top leans toward the Sun (summer), then neither (spring/autumn), then the bottom leans toward the Sun (winter in the north).

Question 8. Describe how seasons are made and reversed between the Northern and Southern Hemispheres.
Answer: Due to the tilted axis of the earth, the Northern Hemisphere gets maximum sunlight from March to September and Southern Hemisphere from September to March. So, the seasons are also reversed e.g. the summer season in Northern Hemisphere correspond by winter in Southern Hemisphere and the spring is exchanged with Autumn season.
In simple words: When the top half of Earth leans into the sunlight, it is summer there, but because the Earth is a ball, that means the bottom half is leaning away into the cold, creating winter there.

Question 9. Distinguish between :
1. Rotation and Revolution
2. Vertical and Slanting Rays.
3. Equinox and Solstice.
4. Twilight and Dawn.
Answer:
(i) Rotation vs Revolution:
(a) Rotation is motion on the axis; Revolution is motion on the orbit.
(b) Rotation takes 24 hours; Revolution takes 365 days.
(c) Rotation causes day/night; Revolution causes seasons.

(ii) Vertical vs Slanting Rays:
(a) Vertical rays fall between the Tropics (\( 23.5^{\circ}\text{ N} \) to \( 23.5^{\circ}\text{ S} \)); Slanting rays fall everywhere else.
(b) Vertical rays are hotter as they are more concentrated; Slanting rays are cooler.

(iii) Equinox vs Solstice:
(a) Equinox means equal day and night; Solstice means unequal day and night.
(b) Equinoxes happen in March/Sept; Solstices happen in June/Dec.

(iv) Twilight vs Dawn:
(a) Twilight is light after sunset; Dawn is light before sunrise.
(b) Twilight is yellowish; Dawn is reddish.
In simple words: These are the different ways Earth's movement and position change how we see light and feel heat.

Practice Questions (Solved)

Question 1. Name the two movements of the Earth.
Answer: Rotation and Revolution.
In simple words: The two ways Earth moves in space.

Question 2. How much time does the Earth take for one revolution?
Answer: 365 days 5 hours 48 minutes 46 seconds.
In simple words: Almost exactly one year.

Question 3. State the direction of rotation of Earth.
Answer: West to East.
In simple words: It spins toward the right side of a map.

Question 4. Name the longest day in the Northern Hemisphere.
Answer: 21st June.
In simple words: The peak of summer.

Question 5. Name the shortest day in the Northern Hemisphere.
Answer: 22nd December.
In simple words: The middle of winter.

Question 6. Name the longest day in the Southern Hemisphere.
Answer: 22nd December.
In simple words: When we have winter, they have their longest summer day.

Question 7. Name the shortest day in the Southern Hemisphere.
Answer: 21st June.
In simple words: When we have summer, they have their shortest winter day.

Question 8. On what dates are the days and nights equal throughout the world ?
Answer: 21st March and 23rd September.
In simple words: The two days of the year when light and dark are balanced for everyone.

Question 9. At which latitude, is the Sun overhead on 21st June ?
Answer: 23 1/2° North.
In simple words: This is the Tropic of Cancer.

Question 10. At which latitude is the Sun overhead on 22nd – December?
Answer: 23 1/2° South.
In simple words: This is the Tropic of Capricorn.

Question 11. Name the two ends of the Axis of the Earth.
Answer: North pole and South Pole.
In simple words: The top and bottom "tips" of the Earth.

Question 12. What is the speed of rotation at the equator ?
Answer: 1600 km per hour.
In simple words: You are spinning faster than a speeding bullet right now, even though you can't feel it!

Question 13. Which country is known as the land of the ‘midnight Sun’?
Answer: Norway.
In simple words: A country so far north that the sun stays up all night in summer.

Question 14. Which country is known as the land of the rising Sun?
Answer: Japan.
In simple words: It is one of the easternmost countries, so it sees the new day's sun first.

Question 15. What does the word equinox mean ?
Answer: Equal nights.
In simple words: A day where the night is just as long as the day.

Question 16. We always see the Sun rising in the East. Why ?
Answer: Because the Earth rotates from West to East.
In simple words: Because the world spins that way, the Sun comes into view from the East.

Question 17. What the word ‘Solstice mean’?
Answer: It means the Sun standing still.
In simple words: It’s the moment the Sun reaches its highest or lowest point and seems to pause before heading back the other way.

Question 18. When does the summer solstice occur ?
Answer: On 21st June.
In simple words: The longest day of the year in the Northern half.

Question 19. When does the winter solstice occur ?
Answer: On 22nd December.
In simple words: The shortest day of the year in the Northern half.

Question 20. When is the spring equinox ?
Answer: On 21st March.
In simple words: The day spring officially begins.

Question 21.
(a) What do you mean by “Rotation of Earth” ?
(b) What are its effects ?
Answer:
Rotation: The earth rotates (turns) round its axis from west to east once in twenty four hours. This motion is called the Daily Motion or Rotation.
Its effects :
1. Day and night’s are caused.
2. The sun, the moon and the star appear to move from east to west.
3. Winds and currents changes their direction.
4. Different places have different local times.
5. Tides occur regularly twice a day.
In simple words: Rotation is Earth's spin. It gives us our day, makes the stars seem to move, and keeps the oceans and winds moving.

Question 22. Give reasons for the following statements :
(a) The Sun does not rise at the same time everywhere in the world.
(b) The speed of rotation at Leningrad (60°N), Genoa (45°N) and Singapore (0°N) along the Earth’s axis is not the same.
(c) We do not feel the great speeds of Earth’s rotation in day-to-day life.
Answer:
(a) Because Earth is a sphere, not a flat disc; different places enter the sunlight at different moments as it spins.
(b) Because of the spherical shape of the earth, the distance around the planet is largest at the equator (\( 0^{\circ} \)) and smaller at higher latitudes.
(c) Because the land, water and the air around the Earth are moving as a whole at a constant speed.
In simple words: Earth's round shape and the fact that we move *with* it explain why we see the Sun at different times and why we don't feel like we are flying through space.

Question 23. Give reasons for the following statements :
(a) The areas, lying on the Equator, have their duration of day-light almost constant throughout the year.
(b) The duration of day and night is equal everywhere on 21st March and 23rd September.
(c) Daylight decreases as we go polewards from March 21st to June 21st in the Southern Hemisphere.
(d) Beyond the tropics, the Sun is never overhead.
(e) On the 22nd of December, the altitude of the midday Sun at Colombo is different from that of Delhi.
(f) The regions, near North Pole and South Pole, have six months of continuous day-light and darkness.
Answer:
(a) The circle of illumination always cuts the equator into two equal parts regardless of the tilt.
(b) On these equinoxes, the mid-day sun is overhead at the equator, so both hemispheres face the sun equally.
(c) In the Southern Hemisphere, the Earth is leaning away from the sun as it moves toward June 21st.
(d) Because the Earth's tilt only allows the Sun to reach a \( 90^{\circ} \) angle between the two Tropics.
(e) Delhi is much further from the Tropic of Capricorn than Colombo is, so the Sun’s angle is much lower in Delhi.
(f) Due to the fixed tilt of the axis, for half the year, the Pole is tilted entirely into the light, and for the other half, entirely into the dark.
In simple words: These are all results of the Earth's \( 23.5^{\circ} \) tilt and its trip around the Sun.

Question 24. Give reasons for the following :
(a) Twilight is of longer duration in higher latitudes than at Equator.
(b) Altitude of the Sun varies at a place according to seasons.
(c) Seasons are reversed between Northern and Southern Hemisphere.
(d) The duration of day and night is equal everywhere in the world on 21st March.
(e) Tropical latitudes are the hottest part of the’Earth.
(f) The period of Twilight and Dawn increases polewards.
(g) 25th of December (Christmas) in New Zealand may be one of the hottest days of the year.
(h) Noon is hotter than morning.
(i) Vertical rays are hotter than slanting rays.
(j) There is no Twilight and Dawn on the Equator.
(k) Sun rises on the east.
(l) Norway is called the land of the Midnight Sun.
(m) The speed of the rotation of the earth is greater at the Equator than at the Arctic Circle.
(n) Winds are deflected to the right in Northern Hemisphere and to the left in Southern Hemisphere.
(o) The variation in the lengths of day and night goes on increasing polewards.
Answer:
(a) In low latitudes, the Sun’s path is almost vertical and sinks rapidly. In high latitudes, the Sun has an inclined path, staying just below the horizon longer.
(b) Because the tilt of the Earth causes the Sun’s "migration" between different latitudes throughout the year.
(c) The tilt of \( 23.45^{\circ} \) causes one hemisphere to lean toward the sun while the other leans away.
(d) The sun falls vertically on the equator, and the circle of illumination passes through both poles.
(e) This belt receives the most direct, vertical heat from the overhead Sun.
(f) Sunlight is limited at high latitudes and the Sun stays near the horizon longer.
(g) In December, the Southern Hemisphere (where NZ is) is tilted most toward the Sun.
(h) Sun rays are vertical at noon, covering less distance through the atmosphere.
(i) Vertical rays are focused on a small area; slanting rays spread the same energy over a wide area.
(j) The Sun’s path is almost perfectly vertical, so it moves through the horizon zone instantly.
(k) Earth rotates West to East.
(l) Northern Norway is within the Arctic Circle where summer days last 24 hours.
(m) The Earth's circumference is greatest at the equator, requiring more speed to finish a turn in 24 hours.
(n) This is the Coriolis Force caused by the Earth’s rotation.
(o) The circle of illumination is widest at the equator and tapers toward the poles.
In simple words: This giant list explains everything from why the wind blows to why Christmas can be hot. It all comes back to Earth being a tilted, spinning ball orbiting the Sun.

Question 25. What is Midnight Sun ? Where does it shine ?
Answer: In summer (around June 21st), the sun never sets at the Arctic Circle and shines for all 24 hours. This includes parts of Alaska, Northern Europe, and Norway (especially Hammerfest). In Antarctica, it happens around December.
In simple words: It’s when the Sun stays in the sky even at night. It only happens at the very top or bottom of the world.

Question 26. Why are there seasons on earth ?
Answer: Seasons are caused by the inclination of the earth’s axis at \( 66.5^{\circ} \) to its orbital plane combined with its revolution. This tilt causes different parts of Earth to receive different amounts of light and heat at different times of the year. If Earth did not tilt, there would be no seasons.
In simple words: Seasons happen because Earth leans to one side as it travels around the Sun, making different parts get more or less sunshine.

Question 27. Why are days longer than nights in summer ?
Answer: During summer, the pole for that hemisphere is tilted toward the sun, which exposes a larger area of that hemisphere to sunshine. This means more of the latitude circles stay on the lighted side for a longer part of the 24-hour spin.
In simple words: Because your half of the world is leaning "into" the light, you stay in the sunshine longer before the spin takes you into the dark.

Question 28. Nearness to Sun is normally responsible for hot- weather conditions, but in July earth is farthest from Sun when it is hot in Northern Hemisphere. Why does reverse happen ?
Answer: Due to the tilt in Earth's axis, the Northern Hemisphere is directly exposed to Sun rays in July despite being further away. The distance difference (only 5 million km) is tiny compared to the total distance and is not as important as the angle of the Sun's rays.
In simple words: Tilt is more powerful than distance. Even though we are slightly further away, we are leaning right into the Sun's heat lamp!

Question 29. How is that the opposite seasons are found in Australia and India ?
Answer: India lies in the Northern Hemisphere while Australia lies in the Southern Hemisphere. Due to the inclination of the axis, when one hemisphere leans toward the sun (summer), the other must lean away (winter).
In simple words: When the top of the ball faces the light, the bottom of the ball is hidden in the shade.

Question 30. Why are days and nights equal throughout the world on 21st March and 23rd September ?
Answer: These are equinoxes. The Sun is directly overhead at the equator. Both hemispheres are equally inclined toward the Sun, and the circle of light passes perfectly through both poles, splitting every latitude circle exactly in half.
In simple words: On these days, Earth's tilt is "sideways" to the Sun, so the light hits the planet perfectly evenly.

Question 31. Daylight increases as we go polewards in summer in The Northern Hemisphere. Why ?
Answer: In summer, the Sun is overhead at the Tropic of Cancer. The Northern Hemisphere is inclined towards the Sun, so the circle of illumination cuts the northern parallels unequally, leaving a larger part of the circle in the light. This effect gets stronger as you move North, until you reach the Arctic Circle where it is 24 hours of light.
In simple words: The further North you go in summer, the more you are "peeking" around the curve of the Earth into the Sun's rays.

Question 32. Account for the unequal length of day and night.
Answer: This is due to two reasons:
(a) The inclination of the axis.
(b) The revolution of the Earth.
Because of the tilt, one half of the world leans into the light for six months while the other leans away. If the axes were vertical, days and nights would be 12 hours everywhere, always.
In simple words: The tilt and the trip around the Sun mean the "light part" of our spin changes size throughout the year.

Question 33. What are the effects of the inclination of the axis ?
Answer:
(a) Apparent movement of the Sun between the tropics.
(b) Opposite seasons in the two hemispheres.
(c) Variation in the length of day and night.
(d) Alternate exposure of the two poles to the Sun's rays (6 months day/night).
In simple words: The lean of the Earth is why the Sun seems to move in the sky, why we have winter and summer, and why days get longer or shorter.

Question 34. What are the results of the difference in the Earth’s speed of rotation at various latitudes ?
Answer: The difference in speed affects the circulation of the atmosphere and oceans. Winds and currents are deflected (Coriolis Effect/Ferrel's Law)—to the right in the North and left in the South. It also causes the Earth to be flattened at the poles and bulge at the equator.
In simple words: The speed difference acts like a giant force that steers the wind and waves and gives Earth its slightly squashed shape.

Question 35. Distinguish between the following pairs :
(a) Summer Solstice and Winter Solstice.
(b) Solstice and Equinoxes
Answer:
(a) Summer vs Winter Solstice (North):
1. Summer: June 21; Winter: Dec 22.
2. Summer: Sun over Tropic of Cancer; Winter: Sun over Tropic of Capricorn.
3. Summer: Longest day; Winter: Shortest day.

(b) Solstices vs Equinoxes:
1. Solstices: Sun at Tropics; Equinoxes: Sun at Equator.
2. Solstices: Max difference in day/night; Equinoxes: Equal day/night.
3. Solstices: Extreme heat/cold; Equinoxes: Mild spring/autumn.
In simple words: Solstices are the peaks of the seasons, and Equinoxes are the transition points between them.

Question 36.
(a) Define Rotation
(b) What is the period of rotation?
(c) What are its effects ?
Answer:
(a) Rotation is the spinning of the Earth on its axis from West to East.
(b) The period is 23 hours 56 minutes 4 seconds (approx 24 hours).
(c) Effects include: 1. Day and night, 2. Apparent movement of stars, 3. Tides, 4. Wind/current deflection, 5. Time measurement, 6. Determining the four directions.
In simple words: Earth's spin is our daily clock. It gives us light and dark and helps us know which way is North, South, East, and West.

Question 37.
(a) What is revolution ?
(b) What is period of revolution ?
(c) What are aphelion and perihelion ?
(d) What are its effects ?
Answer:
(a) Revolution is the spinning of the Earth around the sun in an elliptical orbit.
(b) 365 1/4 days.
(c) Aphelion: Earth farthest from Sun (July, 152m km); Perihelion: Earth nearest Sun (Jan, 147m km).
(d) Effects: 1. Seasons, 2. Day/night length variation, 3. Sun's changing altitude, 4. 6-month days at poles, 5. Solar energy distribution.
In simple words: Revolution is Earth's yearly lap around the Sun. It creates our calendar and our seasons.

📝 Teacher's Note: Make sure students understand that Perihelion happens in winter for us in the Northern Hemisphere, proving tilt is more important than distance for temperature.

🎯 Exam Tip: When listing effects, "Season change" is the most important keyword.