🌍 Chapter 21: Space & Environment – Short Questions
Prepared by Muhammad Tayyab, Subject Specialist Physics, Govt Christian High School Daska. Based on PECTAA 2026 syllabus (National Curriculum 2023).
📖 What's Inside: This section covers all 43 short questions from Chapter 21 Space and Environment including Sun and nuclear fusion, orbital distance and period, cyclones and Coriolis effect, global warming and its impacts, geothermal activity, background radiation sources, and radiation safety. Each question is presented with a precise answer as per the official PECTAA 2026 Physics curriculum. Perfect for Punjab Boards (Lahore, Gujranwala, Multan, etc.) and all BISE boards across Pakistan.
📚 Related Resources – Chapter 21
Space and Environment covers the Sun, nuclear fusion, orbital mechanics, cyclones, global warming, background radiation, and radiation safety.
📑 Quick Jump to Questions
📝 Short Questions with Answers
1 What is the Sun? What keeps planets orbiting around the Sun?
Answer: The Sun is the greatest source of light, heat and other forms of electromagnetic (E.M) waves. The gravitational pull of the Sun keeps planets, including the Earth to orbit around it. It is located at the centre of our solar system.
✅ Sun: source of light & heat; gravitational pull keeps planets in orbit.
2 What is the composition of the Sun?
Answer: The Sun contains 74% of hydrogen and 24% of helium along with few other elements.
✅ 74% Hydrogen, 24% Helium.
3 What happens at the core of the Sun?
Answer: Nuclear fusion takes place at the core of the Sun, in which hydrogen atoms are fused together to form helium, resulting in a tremendous increase in the temperature of the Sun.
✅ Nuclear fusion: hydrogen → helium, releasing immense energy.
4 In what forms does the energy released from the Sun travel through space?
Answer: The energy released from the Sun travels through space in the form of various types of radiations such as infrared, heat, sunlight and ultraviolet radiations.
✅ Infrared, heat, sunlight, ultraviolet radiations.
5 What is orbital distance?
Answer: Orbital distance is the distance of a planet from the Sun. Planets closer to the Sun have smaller orbital distances, while those farther away have larger orbital distances.
✅ Distance of a planet from the Sun.
6 What is orbital period?
Answer: This is the time a planet takes to complete one orbit around the Sun. Planets closer to the Sun have shorter orbital periods.
✅ Time for one complete orbit around the Sun.
7 What does density reflect about a planet? OR Why do rocky planets have higher densities than gas giants?
Answer: Density reflects a planet's composition. Rocky planets like Earth and Mars have higher densities due to their solid, metallic cores, while gas giants like Jupiter and Saturn have lower densities because they are composed mostly of hydrogen and helium.
✅ Density reflects composition: rocky = dense, gas giants = less dense.
8 What factors affect the surface temperature of a planet?
Answer: Surface temperature depends on factors like distance from the Sun, atmospheric composition, and greenhouse effects.
✅ Distance from Sun, atmospheric composition, greenhouse effects.
9 Why is Venus so hot while Mars is so cold?
Answer: Venus is very hot due to its thick, heat-trapping atmosphere, while Mars is much colder due to its thin atmosphere and greater distance from the Sun.
✅ Venus: thick atmosphere traps heat; Mars: thin atmosphere, farther from Sun.
10 What does the gravitational field strength of a planet depend on?
Answer: For a planet, the gravitational field strength at its surface depends on its mass, and is nearly uniform across its surface. The strength of the gravitational field decreases as the distance from the planet increases.
✅ Depends on planet's mass.
11 How does a planet's size affect its gravitational force?
Answer: Smaller planets (like Mars) have a weaker gravitational force, while larger planets (such as Jupiter) have a stronger gravitational force relative to Earth.
✅ Larger planets = stronger gravitational force.
12 What are cyclones?
Answer: Cyclones refer to heavy storms containing fast and spinning winds forming around low air pressure area.
✅ Heavy storms with fast spinning winds around low pressure.
13 What phenomenon is responsible for the development of cyclones?
Answer: The phenomenon of convection is responsible to develop these cyclones. The convection takes place due to rise of the warm air (being lighter) as compared to the (heavier) cool air that moves down.
✅ Convection: warm air rises, cool air moves down.
14 What is the Coriolis effect?
Answer: Because the Earth is spinning, this moving air does not go in a straight line. Instead, it starts to spin around the low-pressure area. This effect is called the Coriolis effect.
✅ Spinning of air around low-pressure due to Earth's rotation.
15 What is the eye of a cyclone?
Answer: In the middle of the cyclone, a special area called the eye forms, where the air moves downward, making it calm and clear.
✅ Central calm area of cyclone.
16 How does the cyclone weaken?
Answer: Cyclones start to weaken when they move over land or colder water because they can no longer get warm, moist air, which acts like fuel for the storm.
✅ Lose warm, moist air (fuel) over land or cold water.
17 What is global warming?
Answer: Global warming is a long-term increase in the average surface temperature of the Earth due to burning of fossil fuels, release of gases like methane, carbon dioxide and nitrous oxide, cutting down forests, and certain industrial and farming methods. Impact: The global warming has a great impact on the weather, sea level and disruptions to ecosystems.
✅ Long-term increase in Earth's average surface temperature.
18 What is geothermal activity?
Answer: Geothermal activity refers to the inner heat of the Earth, which causes volcanic eruptions, geysers, hot springs, and the movement of tectonic plates.
✅ Inner heat of Earth causing volcanoes, geysers, hot springs.
19 Why is geothermal energy considered a renewable resource of energy?
Answer: Geothermal energy is considered as renewable resource of energy due to its sustainability as long as the Earth's internal heat remains active.
✅ Renewable as long as Earth's internal heat remains active.
20 How does global warming affect hurricanes?
Answer: Due to rise in the temperature, more heat is absorbed by the ocean which fuels hurricanes, making them stronger and more destructive. Intensity of hurricanes is increased by the warmer ocean waters, with higher wind speeds and heavier rainfall, causing greater damage.
✅ Warmer oceans fuel stronger hurricanes with higher winds and rainfall.
21 How does global warming cause heat waves?
Answer: The rise in the global temperatures produces heat waves. The heat is trapped by the gases in the atmosphere, leading to extended periods of extreme heat.
✅ Rising temperatures trap heat → extended extreme heat periods.
22 How does global warming cause flooding?
Answer: Heavier rainfall comes to a warmer atmosphere because it can hold more moisture, resulting in intense flooding in those areas. As global warming changes weather patterns, storms become stronger, increasing the risk of both inland and coastal floods.
✅ Warmer air holds more moisture → heavier rainfall → flooding.
23 How does global warming contribute to wildfires?
Answer: Wildfires often result from high temperatures and long period of dryness. With reduced moisture in the air and soil, forests and grasslands become more susceptible to ignition.
✅ High temps + dryness → reduced moisture → more ignition.
24 How does global warming cause droughts?
Answer: Due to increase in the temperature, more water evaporates from the land, drying out the soil. This reduces the water available for plants, animals, and people which causes droughts to last longer and become more intense.
✅ Higher temps → more evaporation → drier soil → longer droughts.
25 How can global warming make winter storms stronger?
Answer: Global warming can also make winter storms stronger. Warmer air holds more moisture, which means heavier snowfall when temperatures are cold enough.
✅ Warmer air holds more moisture → heavier snowfall.
26 What is radiation exposure?
Answer: Radiation exposure happens when someone comes into contact with radiation, which is a type of energy. This energy can come from natural sources like the Sun and the ground or from man-made sources like X-ray machines and nuclear power plants.
✅ Contact with radiation energy from natural or man-made sources.
27 Why are safety measures used while working with radiation?
Answer: Too much exposure can harm our bodies by damaging cells. Therefore, safety measures like protective wear and limited exposure are used to stay safe while using radiation for useful purposes.
✅ Too much exposure damages cells; safety measures protect against it.
28 What is background radiation?
Answer: The radiation that exists around us all the time is known as background radiation. It is the constant, low-level ionizing radiation present in the environment from both natural and human-made sources.
✅ Constant low-level ionizing radiation from natural & human-made sources.
29 What are the sources of background radiation? OR What does background radiation include?
Answer: It includes cosmic rays from space, radioactive materials in the Earth's crust (like uranium and radon), and even tiny amounts of radiation in our food and bodies.
✅ Cosmic rays, Earth's crust (uranium, radon), food & bodies.
30 What is radon gas?
Answer: Radon gas is an alpha emitter. It is particularly dangerous if it is inhaled into the lungs in large quantities.
✅ Alpha emitter; dangerous if inhaled in large quantities.
31 What are the properties of radon gas?
Answer: Radon gas is tasteless, colourless and odourless. It is not generally a health issue unless its levels are significantly high.
✅ Tasteless, colourless, odourless.
32 How do rocks and buildings contribute to background radiation?
Answer: Natural radioactivity can be found in building materials, including decorative rocks, stones and bricks. Heavy radioactive elements such as uranium and thorium occur naturally in rocks in the ground.
✅ Natural radioactivity in rocks, stones, bricks (uranium, thorium).
33 How does uranium contribute to background radiation?
Answer: Heavy radioactive elements such as uranium and thorium occur naturally in rocks in the ground. Uranium decays into radon gas.
✅ Uranium decays into radon gas in rocks.
34 How do food and drink contribute to background radiation?
Answer: Food and water contain small amounts of naturally occurring radioactive isotopes, such as potassium-40 and carbon-14. These isotopes are absorbed by plants and animals and enter the human body through consumption.
✅ Potassium-40 and carbon-14 in food and water.
35 What are cosmic rays and how do they contribute to background radiation?
Answer: The Sun and other stars emit an enormous number of cosmic rays including protons. Some enter the Earth's atmosphere at high speeds and, when they collide with molecules in the air, they produce gamma radiation.
✅ Cosmic rays from Sun/stars produce gamma radiation in atmosphere.
36 What can high exposure to radiation cause?
Answer: High exposure to radiation in a short time can cause radiation sickness, with symptoms like nausea, vomiting, fatigue and organ damage.
✅ Radiation sickness: nausea, vomiting, fatigue, organ damage.
37 What is the effect of long-term exposure to low levels of radiation?
Answer: Long-term exposure to low levels of radiation increases the risk of cancer, especially in organs like the lungs, thyroid and bones.
✅ Increased cancer risk (lungs, thyroid, bones).
38 How can radiation affect DNA?
Answer: Radiation can damage DNA, leading to genetic mutations that may affect future generations.
✅ Damages DNA → genetic mutations.
39 How can radioactive materials contaminate the environment?
Answer: Radioactive materials can contaminate air, water, soil and food, spreading radiation to the environment.
✅ Contaminate air, water, soil, food.
40 What is internal exposure to radiation?
Answer: Inhaling radioactive dust or drinking contaminated water can cause internal exposure, where radioactive particles stay in the body and keep emitting radiation.
✅ Inhaling radioactive dust or drinking contaminated water.
41 What can happen if radioactive materials are not stored or handled safely?
Answer: Accidents such as leaks, spills or explosions can occur if radioactive materials are not stored or handled safely.
✅ Leaks, spills, or explosions.
42 How can nuclear power plant accidents and improper waste management affect the environment?
Answer: Nuclear power plant accidents or improper waste management can lead to large-scale disasters, harming communities and ecosystems.
✅ Large-scale disasters, harming communities and ecosystems.
43 How can radioactive materials be misused?
Answer: Radioactive materials can be misused in nuclear bombs, which spread radiation using conventional explosives, causing panic and long-term contamination.
✅ Nuclear bombs spreading radiation via conventional explosives.
🌍 Key Concepts – Space & Environment
\[ E = mc^2 \]
Nuclear Fusion Energy
Nuclear Fusion Energy
\[ F = G\frac{m_1m_2}{r^2} \]
Gravitational Force
Gravitational Force
\[ T \propto \frac{1}{r^2} \]
Solar Energy & Distance
Solar Energy & Distance
Unit 10Thermal Physics
Unit 11Transfer of Thermal Energy
Unit 12Waves
Unit 13Sound
Unit 14Light
Unit 15Electrostatics
Unit 16Electricity
Unit 17Electromagnetism
Unit 18Electromagnetic Induction & EM Waves
Unit 19Electronics
Unit 20Atomic and Nuclear Physics
Unit 21✨ Space and Environment
📖 Complete syllabus coverage for Class 10 Physics (PECTAA 2026) – Units 10 to 21
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus