This MCQ module is based on: Revolution, Seasons and the Tilt of Earth
TOPIC 44 OF 46
Revolution, Seasons and the Tilt of Earth
🎓 Class 7
Science
CBSE
Theory
Ch 12 — Earth, Moon and the Sun
⏱ ~14 min
🌐 Language: [gtranslate]
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[myaischool_lt_science_assessment grade_level="class_7" science_domain="earth_science" difficulty="basic"]
Why Does June Feel Different From December?
In Shimla, Kavya's grandmother keeps two albums: a June album full of apple blossoms and bright T-shirts, and a December album showing the family buried under woollens with snow on the window ledge. Same house, same garden — but the Sun, the air, the length of the day, and even the time of sunset all shift dramatically from one season to the next. Why?
The answer hides in two simultaneous motions of Earth: it spins on its axis (which we studied in Part 1), and at the same time it travels in a big loop around the Sun. That loop is called revolution.
Think first: If Earth's axis were perfectly straight up (no tilt), would every place on Earth get exactly the same amount of sunlight every day of the year? Hold on to this question — you'll answer it by the end of this part.
12.5 Revolution — Earth's Yearly Trip Around the Sun
Besides spinning on its axis every 24 hours, Earth also moves along a huge curved path around the Sun. This motion is called revolution. One complete revolution takes about 365¼ days, which we call one year. The extra quarter day is saved up and added as a 29th of February every 4 years — a leap year.
Orbit: The path along which Earth travels around the Sun is called its orbit. Earth's orbit is not a perfect circle but a slightly stretched oval shape called an ellipse.
12.6 The 23.5° Axial Tilt — The Secret of Seasons
Earth's axis is not straight up and down with respect to its orbit. It is tilted by about 23.5° — as though someone gently nudged the top of the planet sideways. This tilt stays pointing in the same direction in space throughout the whole year. As Earth revolves, this steady tilt means different parts of Earth get tipped toward or away from the Sun at different times of the year.
Key idea: It is not distance from the Sun that causes seasons — it is the tilt. When your half of Earth is tipped toward the Sun, you get summer (long days, high Sun). When it is tipped away from the Sun, you get winter (short days, low Sun).
12.7 Solstices and Equinoxes
Four days in the year are special because of the tilt:
- Summer Solstice (≈ 21 June) — Northern Hemisphere tipped most toward the Sun. Longest day for India, Europe, and the USA; shortest day in Australia.
- Winter Solstice (≈ 22 December) — Northern Hemisphere tipped most away. Shortest day in India; longest day in Australia.
- Spring Equinox (≈ 21 March) — Neither hemisphere tipped more than the other. Day and night are roughly equal (12 hours) everywhere.
- Autumn Equinox (≈ 23 September) — Same balanced tilt; equal day and night again.
| Date | Special name | What happens in India (Northern Hemisphere) |
|---|---|---|
| 21 June | Summer Solstice | Longest day; Sun highest in sky at noon; hottest period |
| 23 September | Autumn Equinox | Day ≈ Night (12 hrs each) |
| 22 December | Winter Solstice | Shortest day; Sun lowest in sky at noon; coldest period |
| 21 March | Spring Equinox | Day ≈ Night (12 hrs each) |
12.8 Why Tilted Sunlight Feels Cooler
When sunlight falls directly overhead, its energy is packed into a small area — the ground heats up fast. When sunlight falls at a slanting angle, the same amount of light is spread over a much larger area, so any single patch of ground receives less energy per second. That is why a winter noon in Delhi feels so much milder than a summer noon, even though the Sun is shining in both cases.
12.9 Climate Zones on Earth
Because the tilt affects different latitudes differently, Earth can be divided into three broad zones:
- Tropical Zone — between the Tropic of Cancer (23.5° N) and Tropic of Capricorn (23.5° S). Sun is often directly overhead. Hot all year. India lies mostly here.
- Temperate Zone — between the Tropics and the Polar Circles. Sun is never directly overhead. Distinct four seasons. Europe, most of USA, China.
- Polar Zone — beyond the Arctic (66.5° N) and Antarctic (66.5° S) Circles. Very slanted sunlight. Extremely cold; has months of continuous daylight in summer and months of darkness in winter.
Activity 12.2 — Model the Tilt with a Ball and a TorchL3 Apply
What you need: a ball (any size), a knitting needle or pencil, a torch (or phone flashlight), a darkened room.
What to do:
- Stick the needle through the ball so it sticks out on both sides — the "axis". Tilt the needle at about 23° from vertical.
- Let a friend hold the torch still in the middle of the room (the Sun).
- Walk slowly in a big circle around the torch, always keeping the needle tilted in the same direction (say, toward the window).
- Stop at four positions on the loop and note which half of the ball receives direct torch light.
Predict: At which point in the loop does the top half (Northern Hemisphere) get more direct light?
When the tilted top of the needle points toward the torch, the top half of the ball catches more direct light — that is the "summer" position for the Northern Hemisphere. Half an orbit later, the top is tilted away and the bottom half gets direct light — that is summer for the Southern Hemisphere (and winter for the North). At the two in-between positions, both halves share equal light — these are the equinoxes.
Competency-Based Questions Mixed L2–L4
Scenario: Kavya's family in Shimla celebrated her birthday on 22 December — the shortest day of the year in India. Her pen-friend Zara lives in Sydney, Australia. Zara wrote that her 22 December felt like peak summer.
Q1. Earth completes one revolution around the Sun in approximately:
(c) 365¼ days. The quarter day adds up to an extra day every 4 years — a leap year.
Q2. By how many degrees is Earth's axis tilted from the vertical to its orbit?
(c) 23.5°. This tilt is the main reason for seasons.
Q3. Explain in 2–3 sentences why 22 December is winter in Shimla but summer in Sydney.
On 22 December the Northern Hemisphere (where Shimla lies) is tilted away from the Sun, so sunlight hits it at a very slanting angle and days are short — giving winter. At the same moment, the Southern Hemisphere (where Sydney lies) is tilted toward the Sun, getting direct sunlight and long days — which is summer.
Q4. Fill in the blank: Most of India lies in the __________ zone, so the Sun is sometimes directly overhead.
Tropical zone. India spans from the Equator roughly up to the Tropic of Cancer (23.5° N).
Q5. If Earth's axis had no tilt at all, which of the following would happen? L4
(b). Without tilt, sunlight would strike every latitude at the same angle throughout the year — no summers, no winters, and equal 12-hour days everywhere.
Assertion & Reason L4 Analyse
Choose: (A) Both A and R true, R explains A. (B) Both true, R does NOT explain A. (C) A true, R false. (D) A false, R true.
A: Places near the Equator do not have a sharp summer or winter.
R: Sunlight at the Equator falls nearly vertically throughout the year.
(A) — because the equatorial belt receives nearly direct sunlight all year, temperature and day length stay fairly steady, and there is no strong summer–winter contrast.
A: Seasons happen because Earth comes very close to the Sun in summer.
R: The Sun is more powerful in summer.
(D) — A is false; seasons are not caused by the small change in distance. They happen because of the 23.5° axial tilt. R is also false; the Sun's output is essentially the same all year.
A: On 21 March and 23 September the length of day almost equals the length of night everywhere on Earth.
R: On these two dates neither hemisphere is tilted toward or away from the Sun.
(A) — both true and R explains A. These are the equinoxes, when the Sun shines directly over the Equator.
Frequently Asked Questions — Revolution, Seasons and the Tilt of Earth
What does the topic 'Revolution, Seasons and the Tilt of Earth' cover in Class 7 Science?
The topic 'Revolution, Seasons and the Tilt of Earth' is part of NCERT Class 7 Science Chapter 12 — Earth, Moon, and the Sun. It covers the key ideas of revolution, seasons, axial tilt, summer, winter, equinox, solstice, orbit, explained through everyday examples, labelled diagrams and hands-on activities drawn from the NCERT Curiosity textbook. Students learn not just definitions but also the reasoning behind each concept so they can answer competency-based questions and assertion–reason items. The lesson helps Class 7 students build a strong base for higher classes by linking each idea to real observations at home, school and in nature, and by preparing them for CBSE school assessments and Olympiads.
Why is 'Revolution, Seasons and the Tilt of Earth' important for Class 7 NCERT Science?
'Revolution, Seasons and the Tilt of Earth' is important because it builds core scientific thinking that Class 7 students will use throughout middle and secondary school. NCERT Chapter 12 — Earth, Moon, and the Sun — introduces revolution and related ideas that appear again in Class 8, 9 and 10 Science. Mastering this subtopic helps students read labels and safety signs, understand news about science and technology, and perform better in CBSE school exams. The chapter also encourages curiosity and evidence-based thinking — skills that support the National Education Policy (NEP) 2020 focus on conceptual understanding and competency-based learning.
What are the key concepts students should remember from Revolution, Seasons and the Tilt of Earth?
The key concepts in 'Revolution, Seasons and the Tilt of Earth' for Class 7 Science are: revolution, seasons, axial tilt, summer, winter, equinox, solstice, orbit. Students should be able to define each term in their own words, give at least one everyday example, and explain how the concept connects to other chapters in NCERT Class 7 Science. For example, linking the idea to daily life — in the kitchen, classroom or outdoors — makes revision easier. Writing short notes, drawing labelled diagrams and solving the NCERT in-text and exercise questions for Chapter 12 will help students retain these concepts for unit tests and the annual CBSE examination.
How is Revolution, Seasons and the Tilt of Earth taught using activities in NCERT Curiosity Class 7?
NCERT Curiosity Class 7 Science teaches 'Revolution, Seasons and the Tilt of Earth' using an inquiry-based approach with Predict–Observe–Explain activities. Students are asked to make a guess first, then perform a simple experiment with safe, easily available materials, and finally explain what they observed. This matches the NEP 2020 focus on learning by doing. For Chapter 12 — Earth, Moon, and the Sun — the textbook includes hands-on tasks, labelled diagrams and questions that build Bloom's Taxonomy skills from Remember (L1) to Create (L6). Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding rather than rote memorisation.
What real-life examples of revolution can Class 7 students observe at home?
Class 7 students can observe revolution at home in many simple ways linked to 'Revolution, Seasons and the Tilt of Earth'. Kitchens, school bags, playgrounds and the night sky are full of examples that connect to NCERT Chapter 12 — Earth, Moon, and the Sun. For instance, students can check labels on food and cleaning products, watch changes while cooking, or observe the Sun and Moon across a week. Keeping a small science diary — noting the date, what was observed and a quick sketch — turns everyday life into a science lab. These real-life connections make concepts stick and prepare students well for competency-based questions in CBSE Class 7 Science.
How does 'Revolution, Seasons and the Tilt of Earth' connect to other chapters of Class 7 Science?
'Revolution, Seasons and the Tilt of Earth' connects to many other chapters in NCERT Class 7 Science Curiosity. The ideas of revolution appear again when students study related topics like heat, light, changes, life processes and Earth-Sun-Moon. For example, understanding this subtopic helps in building mental models for later chapters and for Class 8, 9 and 10 Science. Teachers often use cross-chapter questions in CBSE examinations to test whether students can apply what they learned in Chapter 12 — Earth, Moon, and the Sun — to new situations. This integrated approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.
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