Chapter 14: Rain, Thunder, and Lightning ⛈️
A Comprehensive Guide for PSTET Paper-2 (Science)
Chapter Overview
| Section | Topic | PSTET Weightage | Page No. |
|:---:|:---|::---:|:---:|
| 14.1 | What is a Cloud? How are clouds formed? | Medium | 2 |
| 14.2 | Rain, Hail, and Snow | High | 8 |
| 14.3 | Thunder and Lightning: The Science of Static Electricity | High | 14 |
| 14.4 | Safety during a Thunderstorm (Lightning Conductors) | High | 20 |
| Practice Zone | MCQs & Pedagogical Questions | - | 26 |
Learning Objectives 🎯
After studying this chapter, you will be able to:
✅ Define a cloud and explain the four main processes of cloud formation
✅ Differentiate between various forms of precipitation—rain, hail, snow, sleet, and freezing rain
✅ Explain the scientific principles behind thunder and lightning using static electricity concepts
✅ Describe safety measures to be taken during thunderstorms, including the working of lightning conductors
✅ Apply pedagogical strategies to teach weather phenomena effectively to upper primary students
Pedagogical Link 🔗
For Teachers: This chapter directly aligns with:
Class 7 Science NCERT Chapter 8: "Winds, Storms and Cyclones"
Class 8 Science NCERT Chapter 15: "Some Natural Phenomena"
Teaching Tips:
Begin with students' experiences—ask them to share what they've observed during thunderstorms
Use simple experiments like rubbing a plastic ruler to demonstrate static electricity
Create safety posters with students to reinforce thunderstorm safety rules
Use videos and animations to show cloud formation and lightning strikes (safely)
Connect to local weather—discuss monsoon clouds, hailstorms in your region
Section 14.1: What is a Cloud? How are clouds formed? ☁️
Introduction
Look up at the sky on a sunny day—you might see fluffy white shapes drifting by. On a cloudy day, the sky might be completely gray. But what exactly are these ever-changing formations? A cloud is much more than just "water vapor"—it's a visible collection of tiny water droplets or ice crystals suspended in the air .
14.1.1 What is a Cloud?
Definition: A cloud is a visible aggregate of tiny water droplets or ice crystals (or both) suspended in the atmosphere above the Earth's surface .
Composition:
Clouds are composed of millions of microscopic water droplets (typically 10-20 micrometers in diameter) or ice crystals
These particles are so small and light that they remain suspended in the air, floating on air currents
A single cloud can contain billions of these tiny droplets
📝 PSTET Note: Clouds are not "made of water vapor." Water vapor is invisible. Clouds become visible when water vapor condenses into liquid droplets or ice crystals .
14.1.2 The Basic Science of Cloud Formation
The Fundamental Principle: Clouds form when air containing water vapor rises, cools, and the water vapor condenses on tiny particles in the atmosphere .
The Process Step-by-Step:
Key Requirement: For condensation to occur, the air must reach saturation (relative humidity = 100%). This happens when the air temperature cools to its dew point .
14.1.3 The Four Mechanisms of Cloud Formation
Air can be forced to rise in four main ways. Each mechanism produces different types of clouds .
A. Convectional Lifting ☀️
How It Works:
The Sun heats the Earth's surface unevenly
Air above warm surfaces (like bare ground) becomes warmer and lighter than surrounding air
This warm air rises like a hot air balloon—a process called convection
As it rises, it expands and cools
When it cools to the dew point, condensation occurs, forming clouds
Characteristics:
Produces cumulus clouds (fluffy, cotton-like)
On hot summer days, these can grow into cumulonimbus clouds (thunderstorm clouds)
Common in interiors of continents and near the equator
Classroom Analogy: Think of a hot air balloon—warm air rises because it's lighter. The same happens with pockets of warm air over a hot parking lot or plowed field.
B. Orographic (Mountain) Lifting ⛰️
How It Works:
Air is forced to rise because of physical barriers—mountains or hills
As air moves toward a mountain, it has nowhere to go but up
Rising air cools, condenses, and forms clouds
Characteristics:
Produces clouds on the windward side of mountains (side facing the wind)
The leeward side (opposite side) often remains dry—called a rain shadow
Common along the west coast of India (Western Ghats) and Himalayas
The Foehn Effect: When air descends on the other side of the mountain, it warms up and becomes dry—creating warm, dry winds .
C. Frontal Lifting (Convergence) 🌧️
How It Works:
When two large air masses with different temperatures meet, they don't mix easily
The warmer, lighter air is forced to rise over the colder, denser air
Characteristics:
Produces extensive cloud cover and prolonged precipitation
Common in mid-latitudes where polar air meets tropical air
In India: During monsoon, moist air from the Arabian Sea meets dry air from the northwest, creating lifting and widespread rainfall.
D. Radiative Cooling (Fog Formation) 🌫️
How It Works:
At night, the Earth's surface loses heat through radiation
If cooling brings the air to its dew point, condensation occurs
This creates fog (clouds at ground level)
Characteristics:
Common in winter mornings
Requires clear skies and calm conditions
Dissipates when the Sun warms the ground during the day
14.1.4 Cloud Formation Summary Table
Table 14.1: Cloud Formation Mechanisms
| Mechanism | What Causes Rising | Typical Location | Cloud Types Produced |
|---|---|---|---|
| Convection | Surface heating | Tropical regions, interiors of continents | Cumulus, Cumulonimbus |
| Orographic | Mountains/barriers | Windward side of mountains | Orographic clouds |
| Frontal | Air masses meeting | Mid-latitudes, monsoon regions | Nimbostratus, Cumulonimbus |
| Radiative Cooling | Night cooling | Valleys, low-lying areas | Fog, Stratus |
14.1.5 What's Inside a Cloud?
🌍 Did You Know? Without condensation nuclei (tiny particles in the air), clouds would not form—even when air is supersaturated!
14.1.6 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Cloud Observation Journal | Students observe and sketch clouds daily for a week | Observation skills |
| "Make a Cloud" Experiment | Warm water in jar, ice on top—watch cloud form inside | Hands-on learning |
| Convection Demonstration | Show convection using a hot plate and beaker of water with tea leaves | Visual learning |
| Mountain Model | Use clay to make mountains; spray water to show windward/leeward effect | Model-based learning |
Section 14.2: Rain, Hail, and Snow 🌧️❄️
Introduction
When cloud particles become too heavy to remain suspended in the air, they fall to the earth as precipitation. Precipitation occurs in many forms—rain, snow, hail, sleet, and freezing rain—depending on atmospheric conditions .
14.2.1 From Cloud Droplets to Precipitation
The Size Challenge:
Typical cloud droplet size: 10-20 micrometers (millionths of a meter)
Typical raindrop size: 0.5-5 millimeters (100-250 times larger)
A single raindrop contains the equivalent of 1 million cloud droplets
How Do Droplets Grow? Two main mechanisms explain how tiny cloud droplets become large enough to fall as precipitation .
A. The Bergeron Process (Ice Crystal Process)
Developed by: Tor Bergeron (1933)
Where It Works: Middle and high latitudes, where cloud tops extend above freezing level
How It Works:
Key Fact: At -20°C, when relative humidity is 100% with respect to water, it is about 121% with respect to ice—this drives the process .
B. Collision-Coalescence Process
Where It Works: Tropical "warm clouds" (cloud tops above freezing, no ice crystals)
How It Works:
Factors Favoring Collision-Coalescence:
Great vertical thickness of cloud (more opportunities for collisions)
Abundant moisture
Variation in droplet sizes
14.2.2 Forms of Precipitation
Table 14.2: Major Forms of Precipitation
14.2.3 Detailed Look at Rain, Hail, and Snow
A. Rain 🌧️
Definition: Rain is liquid precipitation with droplet diameter between 0.5 mm and 5 mm .
Formation:
In temperate regions: Most rain begins as snow crystals in cold cloud tops; they melt as they fall through warmer air below
In tropical regions: Rain forms through collision-coalescence in warm clouds
Heavy rain comes from cumulonimbus clouds (thunderstorm clouds)
Rainfall Intensity:
Light rain: Trace to 2.5 mm per hour
Moderate rain: 2.6 to 7.5 mm per hour
Heavy rain: > 7.5 mm per hour
B. Snow ❄️
Definition: Snow is precipitation in the form of ice crystals (snowflakes) .
Formation:
Requires subfreezing temperatures throughout the cloud and most of the path to the ground
Ice crystals form and grow through vapor deposition (Bergeron process)
Crystals aggregate (stick together) to form snowflakes
Shape, size, and concentration vary with formation conditions
Factors Affecting Snow Formation:
🌍 Did You Know? No two snowflakes are exactly alike—the incredible variety comes from different temperature and humidity conditions during formation.
C. Hail 🧊
Definition: Hail is precipitation in the form of hard, irregular lumps of ice .
Formation (Requires Cumulonimbus Clouds):
Hail Size:
Pea size: 5-10 mm
Marble size: 10-20 mm
Golf ball size: 40-50 mm
Record: 20 cm diameter (largest recorded)
Conditions for Hail:
Strong updrafts
Cloud top well above freezing level
Large temperature difference between cloud base and top
📝 PSTET Note: Hail forms ONLY in cumulonimbus clouds with strong updrafts—not in ordinary rain clouds.
14.2.4 Types of Precipitation Based on Formation
| Type | Cause | Characteristics |
|---|---|---|
| Convectional Precipitation | Surface heating → convection | Localized, heavy, short duration; common in tropics and summer afternoons |
| Orographic Precipitation | Air forced over mountains | Windward side gets heavy rain; leeward side rain shadow |
| Frontal/Cyclonic Precipitation | Warm air rises over cold air at fronts | Widespread, prolonged; common in mid-latitudes and monsoon |
14.2.5 What Determines Rain, Hail, or Snow?
Table 14.3: Factors Determining Precipitation Type
| Factor | Rain | Snow | Hail |
|---|---|---|---|
| Cloud type | Nimbostratus, Cumulonimbus | Nimbostratus, Altostratus | Cumulonimbus |
| Liquid water content | Moderate/High | Low | Very high |
| Height of 0°C line | Well above ground | At or below ground | Within cloud (multiple freezing levels) |
| Updrafts | Weak/Moderate | Weak | Strong |
| Season | Any | Winter | Spring/Summer (strong convection) |
Virga: Sometimes precipitation evaporates before reaching the ground, especially in dry climates. This is called virga .
14.2.6 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Water Cycle Model | Create model showing evaporation, condensation, precipitation | Visual learning |
| Hail Investigation | If hailstorm occurs, collect hailstones (safely), measure size, cut to see layers | Real-world science |
| Rain Gauge Activity | Make simple rain gauge and measure rainfall over time | Hands-on measurement |
| "Why Snow?" Discussion | Discuss why some places get snow and others only rain | Critical thinking |
Section 14.3: Thunder and Lightning: The Science of Static Electricity ⚡
Introduction
A thunderstorm is one of nature's most spectacular displays—brilliant flashes of lightning, crashes of thunder, and sometimes hail and heavy rain. But what causes these dramatic phenomena? The answer lies in static electricity .
14.3.1 What is Lightning?
Definition: Lightning is a huge electric spark that occurs in the atmosphere between oppositely charged regions within a cloud, between two clouds, or between a cloud and the ground.
Key Fact: Lightning is essentially a giant version of the tiny spark you get when you touch a metal doorknob after walking on a carpet!
14.3.2 How Static Electricity Builds Up in Clouds
A. Charging Mechanisms
Inside a thunderstorm cloud (cumulonimbus), violent air movements cause charge separation .
The Process:
Result: The cloud becomes a giant electric dipole—positively charged at the top, negatively charged at the bottom.
B. The Role of Turbulence
Recent research shows that turbulence inside storms plays a crucial role in enhancing charge buildup :
Turbulence increases the rate at which particles collide
More collisions mean more charge transfer
In snowstorms (thundersnow), turbulence can build up charge without needing a pre-existing electric field
14.3.3 From Charge Buildup to Lightning Strike
A. The Electric Field Grows
As charge separation continues, the electric field between the negatively charged cloud base and the positively charged ground (or between cloud layers) becomes incredibly strong.
Comparison:
Normal atmospheric electric field: ~100 V/m
During thunderstorm: Can exceed 3 million V/m (30,000 V/cm)
B. The Breakdown
When the electric field becomes strong enough, it overcomes the insulating properties of air:
| Step | What Happens |
|---|---|
| 1 | Air molecules become ionized (electrons stripped off) |
| 2 | A conductive path (leader) forms—stepping down from cloud in invisible steps |
| 3 | When leader nears ground, an upward streamer rises from tall objects |
| 4 | Connection made—return stroke occurs |
| 5 | Massive current flows in fraction of a second |
| 6 | Channel heats to 30,000°C (5 times hotter than Sun's surface!) |
C. Types of Lightning
| Type | Description |
|---|---|
| Intra-cloud | Within same cloud (most common) |
| Cloud-to-cloud | Between different clouds |
| Cloud-to-ground | From cloud to ground (most dangerous to humans) |
| Cloud-to-air | From cloud into clear air |
| Ground-to-cloud | Upward lightning from tall structures |
14.3.4 What Causes Thunder?
Definition: Thunder is the sound produced by rapidly expanding air along the path of a lightning bolt.
The Process:
| Step | What Happens |
|---|---|
| 1 | Lightning channel heats to 30,000°C in microseconds |
| 2 | Air in the channel expands explosively (faster than speed of sound) |
| 3 | This creates a shock wave |
| 4 | Shock wave becomes a sound wave—we hear it as thunder |
Why Thunder Rolls:
| Reason | Explanation |
|---|---|
| Distance | Sound from farthest parts of lightning takes longer to arrive |
| Bending | Sound waves bend in atmosphere, causing variations |
| Echoes | Sound reflects off clouds, hills, buildings |
| Multiple strokes | Lightning often has multiple strokes—each creates thunder |
Lightning-Thunder Rule:
Light travels almost instantly (300,000 km/s)
Sound travels slowly (~330 m/s)
Count seconds between flash and thunder, divide by 3 = distance in kilometers
Example: 6 seconds ÷ 3 = 2 km away
14.3.5 Simple Classroom Demonstration
Activity: Making Static Electricity Sparks
| Step | Procedure |
|---|---|
| 1 | Cut a plastic strip about 2.5 cm × 20 cm (1" × 8") |
| 2 | Use clay to stand a large paper clip upright on a table |
| 3 | Wrap a piece of wool (scarf, sweater) around the plastic strip |
| 4 | Quickly pull the plastic through the wool—repeat at least 3 times |
| 5 | Immediately hold the plastic near the top of the paper clip |
| Observation | You hear a snapping sound (mini-thunder) and may see a tiny spark |
Why It Works: Electrons rub off the wool onto the plastic. When enough accumulate, they jump across the air gap to the metal clip. This movement of electrons produces sound waves—the snapping sound .
14.3.6 Important Thunderstorm Facts
| Fact | Details |
|---|---|
| Lightning strikes Earth about 100 times per second | 8 million times per day |
| Temperature of lightning | ~30,000°C (5× Sun's surface) |
| Energy in a single lightning bolt | Could power a home for months |
| Thunder is heard only within ~25 km | Beyond that, sound dissipates |
| "Heat lightning" | Lightning too far away to hear thunder |
14.3.7 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Static Electricity Experiments | Rub balloons, plastic combs—pick up paper pieces | Hands-on learning |
| "Lightning in Your Mouth" | Wintergreen candy crushed in dark creates sparks (triboluminescence) | Engaging demo |
| Distance Calculation Activity | During storm, count seconds between flash and thunder | Real-world application |
| Role Play: Electrons | Students act as electrons moving between clouds and ground | Kinesthetic learning |
Section 14.4: Safety during a Thunderstorm (Lightning Conductors) 🛡️
Introduction
Lightning is powerful and dangerous. Each year, lightning causes injuries, deaths, and significant property damage. Understanding safety measures is essential—both for personal protection and for teaching students .
14.4.1 Why Lightning is Dangerous
| Hazard | Effect |
|---|---|
| Electric shock | Massive current through body—can stop heart, cause burns |
| Fire | Lightning can ignite buildings, trees, forests |
| Explosion | Can ignite flammable materials, damage fuel tanks |
| Power surges | Damage electrical and electronic equipment |
| Secondary injuries | Falls, flying debris from explosion |
14.4.2 Personal Safety During a Thunderstorm
A. The 30-30 Rule
| First 30 | If time between flash and thunder is 30 seconds or less, seek shelter immediately |
|---|---|
| Second 30 | Wait 30 minutes after last thunder before leaving shelter |
B. Safe Locations ✅
| Location | Why Safe |
|---|---|
| Inside a building | Electrical wiring and plumbing provide path to ground; walls provide protection |
| Inside a car (hard-top) | Metal body conducts lightning around occupants to ground (Faraday cage effect)—not because of rubber tyres! |
| Large enclosed structure | Follows same principle as buildings |
C. Dangerous Locations ❌
| Location | Why Dangerous |
|---|---|
| Open fields, hilltops | Tallest object—most likely strike point |
| Under isolated trees | Tree attracts lightning; current can jump (side flash) |
| Near water (swimming, boating) | Water conducts electricity; sweat increases conductivity |
| Open vehicles (convertibles, tractors) | No protection; metal frame exposed |
| Using corded electronics | Current can travel through wires |
| Taking shower/bath | Plumbing conducts electricity |
D. If Caught Outside with No Shelter
| Position | What to Do |
|---|---|
| Crouch low | Reduce height—make smallest target |
| Minimize contact with ground | Crouch on balls of feet—reduce contact area |
| Stay away from tall objects | Move at least twice their height away |
| Spread out | If in group, spread out to reduce multiple casualties |
14.4.3 Lightning Conductors: How They Work
Definition: A lightning conductor (or lightning rod) is a metal rod mounted on a building and connected to the ground through a thick wire, designed to protect the building from lightning damage.
A. Historical Development
| Year | Inventor | Contribution |
|---|---|---|
| 1752 | Benjamin Franklin | Proved lightning is electricity; invented lightning rod |
B. Components of a Lightning Protection System
C. How It Works
Important: Lightning rods do not "attract" lightning significantly. They simply provide a safe path if lightning happens to strike that area.
D. Key Design Requirements
📝 PSTET Note: Down conductors must be spaced correctly to prevent electrical arcing and ensure even current distribution .
14.4.4 Lightning Safety for Schools
14.4.5 First Aid for Lightning Strike Victims
Important: People struck by lightning carry no electrical charge—they are safe to touch!
| Step | Action |
|---|---|
| 1 | Call for emergency medical help immediately |
| 2 | Check breathing and pulse—CPR may be needed |
| 3 | Treat for shock—lay person down, elevate legs if no spinal injury |
| 4 | Check for burns—especially at entry and exit points |
| 5 | Keep person warm |
| 6 | Do NOT move if spinal injury suspected |
14.4.6 Lightning Safety Myths vs. Facts
| Myth | Fact |
|---|---|
| Rubber tyres protect you in a car | Metal frame conducts current around you, not tyres |
| Lightning never strikes same place twice | Empire State Building is struck ~25 times per year |
| If not raining, you're safe | Lightning can strike 10-15 km ahead of storm |
| Lie flat on ground | Crouch low—minimize contact with ground |
| Lightning rods attract lightning | They just provide safe path if strike occurs |
14.4.7 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Safety Poster Project | Students create posters illustrating safety rules | Creative learning |
| School Safety Audit | Students identify safe/dangerous places in school | Real-world application |
| Lightning Conductor Model | Build simple model showing rod, down conductor, ground | Hands-on learning |
| Role Play: Emergency Response | Practice first aid scenario | Life skills |
Chapter Summary: Key Points for Revision 📝
Quick Revision Table
| Topic | Key Points | Common PSTET Questions |
|---|---|---|
| Cloud Formation | Air rises → cools → condenses on nuclei; 4 mechanisms: convection, orographic, frontal, radiative cooling | How are clouds formed? |
| Convection | Surface heating causes warm air to rise; produces cumulus/cumulonimbus | What causes convectional rainfall? |
| Orographic Lifting | Air forced up by mountains; windward side wet, leeward side dry (rain shadow) | Why do Western Ghats get heavy rain? |
| Bergeron Process | Ice crystals grow at expense of supercooled droplets; main precipitation mechanism in temperate regions | Explain Bergeron process |
| Collision-Coalescence | Droplets collide and join; operates in warm tropical clouds | How does rain form in tropical regions? |
| Rain | Liquid droplets 0.5-5 mm | Difference between rain and drizzle |
| Hail | Ice lumps formed in cumulonimbus with strong updrafts; layered structure | How does hail form? |
| Snow | Ice crystals form in cold clouds; remain frozen to ground | Conditions for snowfall |
| Lightning | Static electricity buildup from particle collisions in clouds; opposite charges attract | What causes lightning? |
| Thunder | Explosive expansion of air heated to 30,000°C by lightning | Why do we hear thunder after lightning? |
| Lightning Safety | Indoors safe; avoid open areas, tall trees, water; 30-30 rule | What to do during lightning? |
| Lightning Conductor | Metal rod + down conductor + grounding; protects buildings | How does lightning conductor work? |
Practice Zone: PSTET-Style Questions 🎯
Content-Based MCQs
Q1. Which process of cloud formation is caused by surface heating?
a) Orographic lifting
b) Frontal lifting
c) Convection
d) Radiative cooling
Q2. The Bergeron process of precipitation formation operates in:
a) Warm tropical clouds
b) Cold clouds with ice crystals
c) Fog
d) Dust storms
Q3. Hail is formed in:
a) Stratus clouds
b) Cumulus clouds
c) Cumulonimbus clouds with strong updrafts
d) Nimbostratus clouds
Q4. Lightning is caused by:
a) Collision of warm and cold air
b) Accumulation of opposite electric charges in clouds
c) Heavy rainfall
d) High winds
Q5. The sound of thunder is produced because:
a) Clouds collide with each other
b) Lightning heats air to 30,000°C, causing explosive expansion
c) Raindrops hit the ground hard
d) Wind creates sound waves
Q6. Which of the following is a SAFE place during lightning?
a) Under an isolated tree
b) In an open field
c) Inside a hard-top car
d) Near a swimming pool
Q7. The function of a lightning conductor is to:
a) Attract lightning to the building
b) Provide a safe path for lightning current to reach ground
c) Repel lightning away from the building
d) Store lightning energy
Q8. If you see lightning and hear thunder 9 seconds later, the storm is approximately:
a) 1 km away
b) 3 km away
c) 9 km away
d) 27 km away
Q9. Freezing rain occurs when:
a) Rain falls through subfreezing air near surface and freezes on impact
b) Rain freezes before reaching ground
c) Snow melts and refreezes
d) Cloud droplets freeze
Q10. The process where water vapor condenses directly onto ice crystals in clouds is called:
a) Evaporation
b) Condensation
c) Deposition
d) Melting
Pedagogical MCQs
Q11. A teacher wants to demonstrate static electricity related to lightning. The best activity would be:
a) Show a video of lightning
b) Rub a plastic comb with wool and bring it near small paper pieces
c) Lecture about electrons
d) Draw diagrams on board
Q12. To teach the 30-30 lightning safety rule effectively, a teacher should:
a) Write it on board for students to copy
b) Practice with students by timing pretend lightning-thunder intervals
c) Give a written test
d) Show a PowerPoint slide
Q13. A student asks, "Why does hail have layers like an onion?" The correct explanation is:
a) "It's just how hail looks"
b) Hailstones are carried up and down by updrafts, collecting layers of ice each time
c) "I don't know"
d) Hail forms from frozen raindrops
Q14. While teaching cloud formation, the most effective visual aid would be:
a) Textbook diagram
b) A clear jar with warm water and ice on top to create a cloud
c) List of cloud types
d) Photograph of clouds
Q15. A teacher takes students outside during a light rain to observe cloud types. This is an example of:
a) Lecture method
b) Field observation method
c) Textbook method
d) Laboratory method
Answer Key with Explanations
Pedagogical Reflection for Teachers 🤔
Think-Pair-Share Activity:
Think: How would you explain to students why they should never take shelter under a tree during a thunderstorm?
Pair: Discuss with a colleague how you would design a "Weather Safety Week" for your school with activities for each grade level.
Share: Design a 15-minute activity to teach the difference between convectional, orographic, and frontal rainfall using simple demonstrations or role-play.
NCERT Textbook Linkages 📚
| Class | Chapter | Topic |
|---|---|---|
| Class 7 | Chapter 8 | Winds, Storms and Cyclones |
| Class 8 | Chapter 15 | Some Natural Phenomena |
| Class 9 | Chapter 14 | Natural Resources |
| Class 11 | Chapter 9 | Solar Radiation, Heat Balance and Temperature |
Chapter End Notes
Key Terminology Glossary
Quick Tips for PSTET Aspirants ⚡
✅ Memorize with Mnemonics:
Cloud Formation Mechanisms: "Cows On Farms Relax" = Convection, Orographic, Frontal, Radiative cooling
Precipitation Types: "Rani Sells Hot Samosas Freshly Daily" = Rain, Snow, Hail, Sleet, Freezing rain, Drizzle
Lightning Safety: "Indoors, Car, Crouch" = Indoors safe, Car safe, Crouch if outside
30-30 Rule: "Flash to Thunder 30—get under; wait 30 more—then explore"
✅ Common Exam Traps:
Clouds are NOT made of water vapor—they're made of liquid droplets/ice crystals
Lightning can strike 10-15 km away from rain—"bolt from the blue"
Car safety is due to metal frame (Faraday cage), NOT rubber tyres
Bergeron process operates in cold clouds; collision-coalescence in warm clouds
Freezing rain is different from sleet—freezing rain freezes ON IMPACT
✅ Important Facts:
Lightning temperature: 30,000°C (5× Sun's surface)
Lightning strikes Earth: ~100 times per second
Thunder heard only within: ~25 km
Safe distance rule: 3 seconds = 1 km
Answers to "Check Your Understanding"
[To be filled by student]
📝 Note for Self-Study: After completing this chapter, ensure you can:
Explain the four mechanisms of cloud formation with examples
Describe how precipitation forms (Bergeron and collision-coalescence)
Differentiate between rain, snow, hail, sleet, and freezing rain
Explain how static electricity builds up in thunderclouds
Describe the sequence of events in a lightning strike
Explain why thunder occurs
List 5 safe and 5 unsafe places during lightning
Explain the working of a lightning conductor with diagram
Teach the 30-30 safety rule to students
Perform simple static electricity demonstration
