PAGE 1: How we will learn OVERVIEW ======== Light is what lets us see. In this sub-strand you will identify natural and artificial sources of light, describe ways of lighting a house, and explain why light is used for seeing, for safety and for discouraging some pests. ## Strand 3.0: Force and Energy Sub-strand 3.2: Light Suggested lessons: 14 ## What this sub-strand covers • Sources of light • Ways of lighting the house (windows, translucent roofs, artificial lighting) • Uses of light (to see, safety, discourage pests) ## Source • KICD Grade 4 Science and Technology Curriculum Design (Revised 2024) — Strand 3.0 Force and Energy, Sub-strand 3.2 Light ## Learning outcomes By the end of the sub-strand, the learner should be able to: a) identify the sources of light in nature b) describe ways of lighting a house in day- to- day life c) explain the uses of light in day-to-day life d) appreciate the applications of light in day-to-day life ## Key inquiry questions 1. Why is light important in day-to-day life? ## Learning experiences • brainstorm on the meaning of light • carry out activities to categorise the sources of light in day-to-day life as natural or artificial • discuss with peers the ways of lighting a house • use digital or print media to search for information on sources and uses of light in nature • discuss with peers the applications of light in day- to-day life ## Core competencies • Digital literacy: The learner acquires digital manipulative skills as they interact with technology to search for sources and uses of light in nature. • Communication and Collaboration: The learner contributes to group decision making as they discuss with peers the ways of lighting a house. ## Values • Respect: The learner exercises patience with others opinions as they discuss the applications of light in day-to-day life. ## Pertinent and contemporary issues • Citizenship education: The learner reflects and recorgnise the uses of light for safety and security as they discuss the importance of light. ## Links to other learning areas • Pre-technical Studies: The learner seeks alternative cost-effective ways of lighting a house as they discuss ways of lighting a house. PAGE 2: Lesson 1: What light is — Notes 1 LESSON 1: WHAT LIGHT IS ======================= ## What you will learn • Explain the meaning of light. • State that we see objects when light from them enters our eyes. Curriculum outcomes: a) identify the sources of light in nature ## Introduction Close your eyes in a dark room and you cannot see the desk in front of you. Open a curtain or switch on a lamp and the desk appears. Something has reached your eyes that was missing in the dark. ## Notes Light is a form of energy that enables us to see. We do not see objects by sending sight out of our eyes. Light travels from a source or from an object and enters our eyes. The eyes then help the brain to form a picture. Most objects do not make their own light. A book, a tree and a person are seen because light hits them and some of that light bounces off into our eyes. This bouncing is called reflection. A white shirt reflects more light than a black shirt, so it looks brighter in the same room. ### Where light comes from A source of light is something that gives out light. The sun is the main source of light during the day. At night, or inside a closed room, people use lamps, bulbs, torches or candles. If no light enters the eyes, we cannot see, even if the objects are still there. Darkness is the absence of enough light. It is not a substance that fills the room. ### A first sorting Sources of light can be grouped as natural or artificial. Natural sources are not made by people. Artificial sources are made and used by people. You will sort them carefully in the next lessons. One important warning belongs here: the moon looks bright, but it does not make its own light. It reflects light from the sun. Never look straight at the sun, even if you want to study light. The sun's light is strong enough to damage your eyes. Study sunlight by looking at the things it shines on, not at the sun itself. PAGE 3: Lesson 1: What light is — Brainstorm the meaning of light ## Key words • light — a form of energy that enables us to see • source of light — something that gives out light • reflection — the bouncing of light off an object ## Worked examples ### Example 1 A book on a desk does not glow, but you can see it in the daytime. How is that possible? Working: 1. The book is not a source of light. 2. Light from the sun or a lamp hits the book. 3. Some of that light reflects into your eyes. Answer: Light reflects from the book into the eyes. ## Worked examples ### Example 2 Why can you not see your desk when the room is completely dark? Working: 1. Seeing needs light to enter the eyes. 2. In complete darkness no light is coming from the desk. 3. The desk is still there, but the eyes receive no light from it. Answer: No light from the desk is entering the eyes. ## Activity: Brainstorm the meaning of light You will need: Chalkboard or manila paper, A torch if one is available, A book 1. In a group, brainstorm what the word light means in science. 2. Shine a torch on a book, then cover the torch. Say what changed about seeing the book. 3. Agree on a sentence: light is a form of energy that enables us to see. 4. List three things that give out light and three things that only reflect it. 5. Remind one another not to look directly at the sun. PAGE 4: Lesson 2: Natural sources of light — Notes 1 ## Practice 1. What is light? 2. How do we see a book that does not make its own light? 3. Does the moon make its own light? Explain. ## Answers to practice 1. Light is a form of energy that enables us to see. 2. Light hits the book and reflects into our eyes. 3. No. The moon reflects light from the sun. ## Summary • Light is a form of energy that enables us to see. • We see an object when light from it enters our eyes. • The moon reflects sunlight. It is not a source of light. LESSON 2: NATURAL SOURCES OF LIGHT ================================== ## What you will learn • Identify natural sources of light. • Explain why the sun is the main natural source of light on Earth. Curriculum outcomes: a) identify the sources of light in nature ## Introduction Before anyone switches on a bulb, the world is already lit for much of the day. Plants, animals and people depend on light that nobody built a machine to make. ## Notes A natural source of light gives out its own light and is not made by people. The main natural source of light on Earth is the sun. Sunlight lights homes through openings, helps us see outdoors and is the light green plants use when they make food. The sun is a star. Other stars also give out light. They are so far away that they look like small points in the night sky. Their light is real, but it is too faint to light a house the way the sun does. PAGE 5: Lesson 2: Natural sources of light — What is not a natural source ### Other natural sources - **Lightning** gives a bright flash of light during some storms. It is natural, and it is dangerous. Stay indoors during a thunderstorm. Do not shelter under a lone tree, and stay away from open water. - **Some living things** make a little light in their bodies. Fireflies are insects that can glow. You may not see them where you live. They are still a natural source, even if they are uncommon. - **Very hot objects in nature**, such as molten rock from a volcano, can glow. Most learners will not see this. It is enough to know that great heat can make something give out light. ### What is not a natural source The moon and the planets shine because they reflect sunlight. A shiny sufuria, a mirror and a white wall also reflect light. They are not sources. Clouds look bright when the sun is behind them for the same reason. Daylight changes through the day. It is usually brightest around midday and fades in the evening. We plan outdoor work and games around that natural light, and we still need other sources when the sun has set or when a room stays dark. [DIAGRAM] TYPE: svg ALT: The sun makes light. The moon looks bright because it reflects sunlight. PAYLOAD: CAPTION: The sun makes light. The moon looks bright because it reflects sunlight. [/DIAGRAM] PAGE 6: Lesson 2: Natural sources of light — Find natural light around school ## Key words • natural source — a source of light that is not made by people • sun — the star that is the main source of light on Earth • lightning — a bright flash of light produced in some storms ## Worked examples ### Example 1 Sort these into sources of light and objects that only reflect light: the sun, the moon, a star, a mirror. Working: 1. The sun and other stars give out their own light. 2. The moon and a mirror bounce light that came from somewhere else. 3. Sources: sun and star. Reflectors: moon and mirror. Answer: Sources: the sun and a star. Reflectors: the moon and a mirror. ## Worked examples ### Example 2 Why is the sun called the main natural source of light on Earth? Working: 1. It gives out its own light and people did not make it. 2. It lights the Earth during the day much more strongly than stars, lightning or fireflies. Answer: It is a natural source, and it gives the Earth most of its daylight. ## Activity: Find natural light around school You will need: Exercise book, Pencil 1. Stand in the school compound in the daytime and list what you can see because of sunlight. 2. Move into a classroom and notice where daylight enters. 3. Write three natural sources of light. The sun must be one of them. 4. Write two bright objects that are not sources, such as the moon or a mirror, and say that they reflect light. 5. Share one safety rule about lightning or about not looking at the sun. PAGE 7: Lesson 2: Natural sources of light — Answers to practice ## Practice 1. Name three natural sources of light. 2. Why is a mirror not a source of light? 3. Give one safety rule during lightning. ## Answers to practice 1. The sun, other stars, and lightning. Fireflies are also a natural source. 2. A mirror does not make light. It reflects light from a source. 3. Stay indoors, or do not shelter under a lone tree, and keep away from open water. ## Summary • The sun is the main natural source of light on Earth. • Stars, lightning and some living things such as fireflies also give out light. • The moon reflects sunlight. It is not a source of light. LESSON 3: ARTIFICIAL SOURCES OF LIGHT ===================================== ## What you will learn • Identify artificial sources of light used in day-to-day life. • Compare a source that makes light with an object that only reflects it. Curriculum outcomes: a) identify the sources of light in nature ## Introduction When the sun sets, people still cook, read and walk home. They use light that someone has made: a bulb, a lamp, a candle or a torch. ## Notes An artificial source of light is made and controlled by people. We use these sources at night, in dark rooms, and whenever daylight is not enough. PAGE 8: Lesson 3: Artificial sources of light — Common artificial sources ### Common artificial sources - **Electric bulbs** light many homes, classrooms and streets. An LED bulb uses less electricity than an old filament bulb and usually lasts longer. - **Torches**, including a phone torch, give a beam of light that we can point. They are useful on a path at night. - **Candles** burn wax and a wick. They give a small flame. - **Kerosene lamps and pressure lamps** burn fuel to make a flame. They light a room where there is no electricity, but the smoke is not good to breathe for a long time, and a knocked lamp can start a fire. - **Cooking fires and gas flames** give light as well as heat. A fire lit by people is an artificial source. - **Solar lamps** store energy from sunlight in the day and give light at night. The lamp is made by people, so it is an artificial source, even though it uses the sun. A vehicle headlamp, a security bulb and the screen of a torch are also artificial sources. ### Care with flames Candles, kerosene lamps and open fires can burn people and buildings. Put them on a firm surface, away from curtains, paper and bedding. Do not leave a flame burning in an empty room. An adult should light them. Electric bulbs also get hot. Do not touch a lit bulb with bare fingers. Artificial light is a tool. It lets us work after sunset, but it should be used safely and switched off or put out when it is not needed. ## Key words • artificial source — a source of light made and used by people • LED bulb — a kind of electric bulb that uses less electricity than an old filament bulb • solar lamp — a lamp that stores energy from sunlight and gives light later ## Worked examples ### Example 1 A family uses a solar lamp at night. Is the lamp a natural source or an artificial source? Working: 1. People made the lamp and switch it on. 2. It uses sunlight, but the lamp itself is not a natural object like the sun. 3. It is an artificial source of light. Answer: An artificial source ## Worked examples ### Example 2 Why is a kerosene lamp both useful and risky? Working: 1. The flame gives light where there may be no electricity. 2. The lamp can be knocked over and the fuel can catch fire. 3. The smoke is also unpleasant to breathe. Answer: It gives light, but it can cause a fire and its smoke is harmful to breathe for a long time. PAGE 9: Lesson 3: Artificial sources of light — Answers to practice ## Activity: List the lights people make You will need: Exercise book, Pictures of bulbs, torches, candles and lamps from the textbook 1. Look at the pictures and name each artificial source. 2. Add any source used in your own home, such as a bulb, a solar lamp, a candle or a phone torch. 3. Next to each one, write one good use and one safety rule. 4. Discuss which sources need a flame and which use electricity. 5. Take turns to report one source to the class. ## Practice 1. What is an artificial source of light? 2. Name four artificial sources of light. 3. Give two safety rules for using a candle. 4. Why is an LED bulb often a better choice than an old filament bulb? ## Answers to practice 1. A source of light that is made and used by people. 2. Any four: electric bulb, torch, candle, kerosene lamp, solar lamp, cooking fire, vehicle headlamp. 3. Put it on a firm surface away from curtains and paper, and do not leave it burning in an empty room. An adult should light it. 4. It uses less electricity and usually lasts longer. ## Summary • Artificial sources are made by people, such as bulbs, torches, candles and lamps. • Flames need an adult and a safe place. • Switch lights off or put flames out when they are not needed. LESSON 4: SORTING SOURCES OF LIGHT ================================== ## What you will learn • Categorise sources of light as natural or artificial. • Explain mistakes people make when sorting sources. Curriculum outcomes: a) identify the sources of light in nature ## Introduction A learner writes the moon under natural sources and a candle under natural sources too. One of those choices mixes up a reflector with a source. The other forgets that people make candles. PAGE 10: Lesson 4: Sorting sources of light — Easy mistakes ## Notes Sorting sources of light means putting each one in the right group. Use two questions. 1. Does it give out its own light, or does it only reflect light? 2. If it gives out light, did people make it, or is it part of nature? If it only reflects, it is not a source at all. If people made it, it is artificial. If nature produces it, it is natural. ### A sorting guide **Natural sources:** the sun, other stars, lightning, fireflies and other living things that glow. **Artificial sources:** electric bulbs, torches, phone lights, candles, kerosene lamps, pressure lamps, gas lamps, cooking fires lit by people, vehicle lamps and solar lamps. **Not sources:** the moon, planets, mirrors, shiny metal, white walls and clouds. They can look bright, but the light began somewhere else. ### Easy mistakes - Calling the moon a source because it is in the sky. Place is not the test. Making light is the test. - Calling every fire natural. A fire people light for cooking is artificial. Lightning is natural. - Calling a solar lamp natural because it uses the sun. The sun is natural. The lamp people built is artificial. - Calling a window a source. A window lets light through. It does not make light. When you categorise, write the name of the object and the group. Then add a short reason. That reason shows you understand the groups, not only the names. ## Key words • categorise — to sort things into groups • reflector — an object that bounces light but does not make it ## Worked examples ### Example 1 Categorise these: lightning, a candle, the moon, a torch. Working: 1. Lightning gives its own light and people do not make it, so it is natural. 2. A candle and a torch are made by people, so they are artificial. 3. The moon only reflects sunlight, so it is not a source. Answer: Natural: lightning. Artificial: candle and torch. Not a source: the moon. PAGE 11: Lesson 4: Sorting sources of light — Answers to practice ## Worked examples ### Example 2 A learner says a clean window is a source of light. What is the mistake? Working: 1. A window lets daylight into a room. 2. The light was made by the sun, not by the glass. 3. The window is a way of lighting a house, not a source. Answer: The window lets light through. It does not make light. ## Activity: Card sort: natural or artificial You will need: Cards or small papers labelled sun, star, lightning, firefly, moon, mirror, bulb, torch, candle, kerosene lamp, solar lamp, window 1. Spread the cards on the desk. 2. Make three columns: Natural source, Artificial source, and Not a source. 3. Place each card and say the reason aloud. 4. Another group checks your columns and you check theirs. 5. Correct any card that was sorted by where it is found instead of by whether it makes light. ## Practice 1. Categorise the sun, a candle and the moon. 2. Why is a solar lamp artificial even though it uses sunlight? 3. What two questions help you sort sources of light? ## Answers to practice 1. The sun is a natural source. A candle is an artificial source. The moon is not a source because it reflects sunlight. 2. People made the lamp. The sun is the natural source. The lamp is a device people use. 3. Does it make its own light or only reflect light? If it makes light, did people make it or is it natural? ## Summary • Natural sources make light and are not made by people. • Artificial sources are made by people. • Reflectors such as the moon and mirrors are not sources of light. LESSON 5: LIGHTING A HOUSE WITH DAYLIGHT ======================================== ## What you will learn • Describe how windows light a house. • Describe how translucent roofs light a house. Curriculum outcomes: b) describe ways of lighting a house in day- to- day life ## Introduction Two houses can stand in the same sunshine and feel very different inside. One is bright enough for reading. The other stays dim until a lamp is lit. The difference is often the openings that let daylight in. ## Notes During the day, the cheapest and safest light in a house is daylight from the sun. People let it in through windows and through some kinds of roofs. PAGE 12: Lesson 5: Lighting a house with daylight — Windows ### Windows A window is an opening in a wall. Glass windows let light in and keep out wind and rain. Some houses have openings with wooden shutters. Open shutters in the daytime let light in. Closed shutters keep a room dark. Clean glass lets in more light than dirty glass. Curtains can be opened when you need light and closed when you need shade or privacy. A room with windows on more than one wall is often brighter than a room with a single small opening. Light from windows helps children read and helps a cook see the food, without using electricity or kerosene. ### Three kinds of materials - **Transparent** materials, such as clear glass, let light through and you can see clearly through them. - **Translucent** materials let light through, but you cannot see clearly through them. Frosted glass and some plastic roofing sheets are translucent. - **Opaque** materials, such as brick, wood and ordinary iron sheets, do not let light through. ### Translucent roofs A translucent roof, or a translucent sheet fixed in part of a roof, lets daylight in from above. Kitchens, corridors, pit latrines and some classrooms use these sheets so the room is brighter in the day. The sheet should be fixed firmly so rain does not leak in. It lights the room while still hiding a clear view of the sky, because you cannot see sharply through a translucent material. Using daylight first is a sensible way to light a house. It does not fill the room with smoke, and it does not need a coin in a meter while the sun is shining. ## Key words • transparent — lets light through and can be seen through clearly • translucent — lets light through, but you cannot see clearly through it • opaque — does not let light through • window — an opening in a wall that lets light and sometimes air into a room PAGE 13: Lesson 5: Lighting a house with daylight — Discuss daylight in a house ## Worked examples ### Example 1 A plastic roofing sheet lets daylight into a kitchen, but people outside cannot see clearly into the room. What kind of material is the sheet? Working: 1. Light passes through the sheet. 2. A clear view does not pass through. 3. A material that lets light through but cannot be seen through clearly is translucent. Answer: Translucent ## Worked examples ### Example 2 Why should classroom windows be kept clean? Working: 1. Dirt blocks some of the daylight. 2. Clean glass lets in more light. 3. Learners can then read without switching on a bulb during the day. Answer: Clean glass lets in more daylight. ## Activity: Discuss daylight in a house You will need: Paper, Pencil, Clear glass or a clean bottle, A book to act as an opaque object, Greaseproof paper or a thin piece of paper if available 1. Hold the clear glass and the book up to the light. Decide which is transparent and which is opaque. 2. If you have thin paper, notice that light comes through but you cannot see a sharp picture. Call it translucent. 3. Sketch a simple house and mark windows and a translucent part of the roof. 4. Discuss with your group how these parts light the house in the daytime. 5. Agree on one way to get more daylight without spending money, such as opening shutters or cleaning glass. PAGE 14: Lesson 6: Artificial lighting in the house — Ways used in homes ## Practice 1. Name two ways of lighting a house with daylight. 2. What is the difference between transparent and translucent? 3. Why is daylight a good first choice for lighting a house? ## Answers to practice 1. Through windows, and through translucent roofs or translucent roofing sheets. 2. Transparent materials let light through and you can see clearly through them. Translucent materials let light through but you cannot see clearly through them. 3. It does not cost money while the sun is shining, and it does not produce smoke like some lamps. ## Summary • Windows let daylight into a house. • Translucent roofs let light through from above without a clear view. • Transparent, translucent and opaque materials behave differently with light. LESSON 6: ARTIFICIAL LIGHTING IN THE HOUSE ========================================== ## What you will learn • Describe artificial ways of lighting a house. • Suggest careful, less wasteful choices for lighting a room. Curriculum outcomes: b) describe ways of lighting a house in day- to- day life ## Introduction Daylight fades in the evening, and some inner rooms stay dim even at noon. Families then choose bulbs, solar lamps, candles or kerosene lamps. The choice affects safety, smoke and how much money is spent. ## Notes Artificial lighting means using a source people control, instead of waiting for the sun. A house may use more than one method. ### Ways used in homes - **Electric lighting.** A switch turns a bulb on and off. One well-placed bulb can light a living area. Lights should be switched off when everyone leaves the room. - **Solar lighting.** A small panel charges a battery in the day. The lamp is used at night. This helps homes that are not connected to the electricity supply. - **Torches.** A torch lights a path, a latrine or a cupboard for a short time. - **Candles and kerosene lamps.** These are common where electricity is off or not available. They need a firm base, ventilation, and an adult nearby. Smoke from kerosene can irritate the eyes and chest. PAGE 15: Lesson 6: Artificial lighting in the house — Example 1 ### Choosing with care Use daylight from windows and translucent sheets before paying for other light. An LED bulb is a careful choice where electricity is used, because it needs less electricity than an old filament bulb. A solar lamp avoids daily kerosene for many families, after the lamp has been bought. Sharing one lamp in a room where people sit together uses less fuel than lighting many candles in empty corners. ### Safety in the house Keep flames away from mosquito nets, curtains, paper and thatch. Do not play near lamps. Do not touch a socket with wet hands. If a bulb is to be changed, an adult should switch off the light first and wait for the bulb to cool. Report a cracked socket or a smoking lamp to an adult. Do not try to repair wiring yourself. Good lighting is bright enough for the job, placed where people need it, and put out or switched off afterwards. ## Key words • artificial lighting — light from sources people control, such as bulbs and lamps • ventilation — letting fresh air move through a room ## Worked examples ### Example 1 A room is bright at noon when the curtains are open, but dark at night. Which lighting is used at noon, and which is needed at night? Working: 1. At noon the light comes through the windows from the sun. 2. At night the sun is not lighting the room. 3. A bulb, solar lamp, candle or kerosene lamp can be used at night. Answer: Daylight through the windows at noon, and artificial lighting at night. ## Worked examples ### Example 2 Suggest two less wasteful ways to light a house. Working: 1. Use free daylight in the daytime by opening windows and cleaning glass. 2. Use an LED bulb or a solar lamp, and switch lights off when leaving a room. Answer: Use daylight in the day, and use an LED bulb or solar lamp only when it is needed. ## Activity: Plan lighting for one house You will need: Paper, Pencil, Textbook pictures of lamps and bulbs 1. Draw three rooms: a sitting room, a kitchen and a latrine or corridor. 2. Mark windows or a translucent roof where daylight can enter. 3. Choose an artificial source for each room at night and write why you chose it. 4. Add one safety rule and one way to avoid wasting fuel or electricity. 5. Compare plans with another group and improve one idea. ## Practice 1. Name three artificial ways of lighting a house. 2. Why should a kerosene lamp not be left near a curtain? 3. What should you do to electric lights when everyone leaves a room? 4. Why might a family choose a solar lamp? PAGE 16: Lesson 7: Light for seeing and for safety — Safety and security ## Answers to practice 1. Any three: electric bulbs, solar lamps, torches, candles, kerosene lamps. 2. The flame can set the curtain on fire. 3. Switch them off. 4. It can give light at night after charging from the sun, which helps where mains electricity is not available and avoids burning kerosene every evening. ## Summary • Houses are lit artificially with bulbs, solar lamps, torches, candles and kerosene lamps. • Use daylight first, then a careful artificial source. • Keep flames away from cloth and paper, and switch lights off when they are not needed. LESSON 7: LIGHT FOR SEEING AND FOR SAFETY ========================================= ## What you will learn • Explain how light helps people see in daily life. • Explain how light is used for safety and security. Curriculum outcomes: c) explain the uses of light in day-to-day life; d) appreciate the applications of light in day-to-day life ## Introduction A cook needs to see the food in a sufuria. A driver needs to see the road. A family feels safer when the path to the gate is lit. Seeing and safety are two of the main uses of light. ## Notes The first use of light is to see. We use it to read, write, cook, sew, find a lost pencil and walk without tripping. In a clinic, a health worker needs light to see a wound. In a workshop, a person needs light to see a tool. Poor light makes reading harder and makes accidents more likely, because people miss steps, knives and holes. Enough light should fall on the work. Reading in a deep shadow strains the eyes. A lamp is more useful on the table where the book is than hidden behind a cupboard. ### Safety and security Light helps people avoid danger and helps them notice strangers or animals near a home. - **Street lights and security lights** light roads, markets and gates at night. - **Headlamps and tail lamps** help drivers see the road and help other road users see the vehicle. - **Reflective clothing and reflectors on bicycles** bounce light from headlamps so a rider can be seen. - **Traffic lights** use colour to direct vehicles and people who are walking. Red means stop. Amber means get ready. Green means go. - **A torch** shows pits, snakes or uneven ground on a night path. Light does not replace other careful habits. You still look both ways before crossing a road. You still lock a door. A security light helps, but it is not a guard by itself. We appreciate light when we remember how many safe actions depend on it: reading a label on medicine, seeing a step, and being seen by a driver. Using light for safety is a way of caring for yourself and for other people. PAGE 17: Lesson 7: Light for seeing and for safety — Search for uses of light ## Key words • safety — being protected from harm • security — being protected from danger or from people who should not enter • reflector — a material that bounces light so a person or bicycle can be seen ## Worked examples ### Example 1 Why should a bicycle ridden at night have a reflector or a lamp? Working: 1. Drivers need to see the bicycle. 2. A lamp gives out light. A reflector bounces the car's light back. 3. Either one helps the rider to be seen, which is a safety use of light. Answer: So that other road users can see the rider. ## Worked examples ### Example 2 A learner reads under a table in deep shadow. Why is this a poor use of light? Working: 1. The book is not receiving enough light. 2. Reading in poor light makes the work harder and can strain the eyes. 3. The lamp or the daylight should fall on the book. Answer: The book does not get enough light, so reading is harder. ## Activity: Search for uses of light You will need: Science textbook or a teacher-approved print page, Exercise book, A digital device only if the teacher supervises it 1. Search the textbook, or a page the teacher opens, for uses of light. 2. Make two columns: To see, and Safety and security. 3. Write at least three examples in each column from home, school or the road. 4. Discuss one accident that poor lighting could cause, and how better light would help. 5. Each learner explains one use in a full sentence. PAGE 18: Lesson 7: Light for seeing and for safety — Answers to practice ## Practice 1. Give three activities that need light so that we can see. 2. How do traffic lights use light for safety? 3. Why is a security light at a gate useful? ## Answers to practice 1. Any three: reading, writing, cooking, sewing, walking at night, finding an object. 2. Red tells road users to stop, amber tells them to get ready, and green tells them to go. 3. It helps the family see the path and notice people or animals near the home at night. ## Summary • Light lets us see in order to read, cook, work and move about. • Street lights, headlamps, reflectors and traffic lights are used for safety. • Light should fall on the work, and it should be bright enough for the job. LESSON 8: PESTS, PLANTS AND OTHER USES OF LIGHT =============================================== ## What you will learn • Explain how light can discourage some pests. • Appreciate other applications of light in day-to-day life. Curriculum outcomes: c) explain the uses of light in day-to-day life; d) appreciate the applications of light in day-to-day life ## Introduction Cockroaches often scatter when a kitchen light is switched on. Green plants grow poorly in a cupboard with no light. Light does more than help people see. It also affects other living things. ## Notes One use of light given in this sub-strand is to discourage pests. Some pests prefer dark hiding places. Cockroaches and rats are often found in dark stores, behind boxes and in unlit corners. A room that is lit, and that does not have deep unused corners piled with rubbish, is less attractive to them. Light alone does not remove every pest. Food should still be covered, rubbish should be taken away, and holes where rats enter should be closed. Light is one part of keeping a kitchen or a store less welcoming to pests that hide in the dark. Some farmers and scientists also use light traps at night. Certain flying insects move towards a lamp. They can be collected there so they do less damage to crops. This is a special use. It is not the same as leaving a bulb on all night in a bedroom. PAGE 19: Lesson 8: Pests, plants and other uses of light — Notes 3 ### Other applications worth appreciating - **Plants** need light to make food in their green leaves. A seedling kept in darkness becomes weak and pale. Putting crops where they receive daylight is an application of light in nature. - **Solar panels** on a lamp or a calculator change light from the sun into electricity. - **Signs and signals** use light so people can follow instructions, as traffic lights do. - **Drying and sorting** some farm produce is easier in good light, because the farmer can see mouldy or damaged grains and remove them. We appreciate light when we use it well: open the windows in the day, light stores and kitchens enough to see and to discourage pests that like darkness, and switch off extra bulbs so electricity is not wasted. Respect other people's ideas when a group discusses which lamp or window plan is best. More than one safe plan can work. ## Key words • pest — a living thing that damages food, crops or health in a home or on a farm • discourage — to make something less likely to stay or happen • solar panel — a device that changes light from the sun into electricity ## Worked examples ### Example 1 Why might lighting a food store help to discourage cockroaches? Working: 1. Cockroaches often hide in dark places. 2. A lit store has fewer dark corners for them to hide in. 3. Light makes the store less attractive to them, together with covering food and cleaning. Answer: Cockroaches prefer dark places, so a well-lit store is less attractive to them. ## Worked examples ### Example 2 A bean seedling is left in a closed cupboard for a week and becomes pale. Which need has not been met? Working: 1. The cupboard is dark. 2. Green plants need light to make food. 3. The seedling lacked light. Answer: The seedling did not get the light it needs to make food. PAGE 20: Lesson 8: Pests, plants and other uses of light — Discuss applications of light ## Activity: Discuss applications of light You will need: Exercise book, Textbook 1. In a group, discuss applications of light: seeing, safety, discouraging pests, helping plants and charging solar lamps. 2. Give each application one real example from daily life. 3. Discuss why a dirty, dark kitchen may have more hiding places for cockroaches than a clean, lit kitchen. 4. Listen to every member before the group chooses its best example. 5. Share that example with the class in one or two sentences. ## Practice 1. How can light discourage some pests in a house? 2. Does a light by itself solve every pest problem? Explain. 3. Why do green plants need light? 4. Name one way a solar lamp uses light. ## Answers to practice 1. Some pests, such as cockroaches and rats, prefer dark places. Lighting rooms and stores makes those places less attractive to them. 2. No. Food should still be covered, rubbish removed and entry holes closed. Light is only one part of the care. 3. They use light to make food in their leaves. 4. A solar panel changes light from the sun into electricity that is stored and used at night. ## Summary • Light can discourage pests that prefer dark places. • Plants need light to make food. • Solar lamps and signals are other useful applications of light. PAGE 21: Revision quiz REVISION QUIZ ============= Answer all the questions, then mark yourself on the Answers tab. 1. Light is a form of energy that enables us to: A. hear B. see C. smell D. float 2. Which of these is a natural source of light? A. A candle B. The sun C. A torch D. A mirror 3. The moon is bright at night because it: A. is a star B. reflects sunlight C. is an electric bulb D. is a fire 4. Which list has only artificial sources of light? A. Sun, star, lightning B. Bulb, candle, torch C. Moon, mirror, window D. Sun, bulb, moon 5. A roofing sheet lets light through but you cannot see clearly through it. The sheet is: A. opaque B. translucent C. a source of light D. a mirror only 6. Which pair shows ways of lighting a house? A. Windows and translucent roofs B. Painting the floor and closing all openings C. Burying lamps and blocking windows D. Removing the roof and the walls 7. Why should a candle be kept away from curtains? A. Curtains reflect too much moonlight B. The flame can set the curtain on fire C. Candles only work outdoors D. Curtains make the candle brighter 8. Traffic lights help safety because: A. red means stop and green means go B. they heat the road C. they remove all vehicles D. they are natural sources 9. Lighting a food store can discourage cockroaches because they: A. only eat bulbs B. prefer dark hiding places C. need traffic lights D. are sources of light 10. Why do green plants need light? 11. Give one reason to appreciate light in daily life. PAGE 22: Quiz answers ANSWERS ======= 1. B. see We see when light enters our eyes. 2. B. The sun The sun makes its own light and is not made by people. A mirror only reflects light. 3. B. reflects sunlight The moon does not make its own light. It reflects light from the sun. 4. B. Bulb, candle, torch Bulbs, candles and torches are made and used by people. 5. B. translucent Translucent materials let light through without a clear view. 6. A. Windows and translucent roofs Windows and translucent roofs let daylight in. Artificial lamps are used as well when daylight is not enough. 7. B. The flame can set the curtain on fire A flame near cloth can start a fire. 8. A. red means stop and green means go The colours tell road users when to stop and when to go. 9. B. prefer dark hiding places Cockroaches often hide in the dark. A lit, clean store is less attractive to them. 10. They use light to make food in their leaves. Without light, green plants cannot make the food they need and they become weak. 11. Light lets us see so we can read, cook and move safely, and it can light paths and gates at night. Seeing and safety are everyday applications of light.