SCHEME OF WORK BASIC SCIENCE JSS 3 FIRST TERM - A-VIBE BLOG
WEEK TOPIC
1.Drug and Substance Abuse
2.Flooding
3.Deforestation and Desertification
4.Bush Burning
5.Depletion of Ozone Layer and its Effects.
6.Resources from living things/Economic Importance of Resource
7.Resources from Non-living Things: Solid Minerals, their Location and Importance
8.Light energy
9.Sound energy
10.Magnetism
WEEK ONE: DRUG AND SUBSTANCE ABUSE
Drug abuse is the excessive use or continuous use of drugs without regard for accepted medical practice. When a drug is used to incite pleasure or escape reality, especially without the doctor’s prescription, is said to be abused.
Substances can also be abused when they are taken beyond acceptable limits. Excess intake of alcohol, cigarette, Marijuana and Indian helm are all example of substance abuse.
HEALTH EFFECTS OF DRUG ABUSE ON YOUTH
Drug and substance abuse has some immediate effects like light headedness, stomach upset, skin rashes, injection abscesses and so on but there are also more chronic effects like:
1.There is a ‘crash’ after the ‘high’ of taking drugs. There is usually fatigue, depression, anxiety and dependence after the drug effect has worn off.
2.Drug abusers easily lose focus.
3.Drug abuse increases the rate of accident because most drugs affect the motor nerves that controls movement of body parts.
4.The aftereffect of some drugs create illusion and hallucinations which terrifies the victim.
5.Unsterilised needles are often used by abusers. This exposes them to a high risk of contacting dangerous disease.
6.Drug overdose often place its victims in coma or a vegetable state unless taken care off.
7.Victim of drug abuse are often violent and found to be psychological unhealthy.
STRATEGIES ON HOW TO LIVE AN HEALTHY DRUG FREE LIFE
1.Always use drugs according to doctor’s prescription.
2.Inculcate positive social interactions and healthy lifestyle.
3.Always reject any invitation to take drugs or substances that are unfamiliar or that are likely to be abuse. Say NO to drug and substance abuse.
4.Avoid going to indecent places (e.g clubs, bar, anti social gatherings) where drug abuse is likely to occur.
ROLES AND ACTIVITIES NATIONAL DRUG CONTROL AGENCY (NDCA)
The Drug control Agencies in Nigeria include:
1.NAFDAC (National Agency for Food and Drug Administration and Control)
2.NDLEA (National Drug Law Enforcement Agency)
The functions of these agencies are as follows:
1.They control the manufacturing of drugs.
2.They monitor sales and distribution of drugs.
3.They refill prescriptions.
4.They care for drug dependent victims.
5.They control of environment conducive to drug abuse development.
6.They research on the method of rehabilitation of drug addict.
7.They educate the general public on the need to avoid drug abuse.
WEEK TWO: FLOODING ELESSON NOTE
Flood is a disastrous overflow of water from a lake or other body of water due to excessive rainfall or other input of water.
When there is heavy rain, so much water flows in=to the rivers that they come over the tops of their banks and flood the land. This can be useful in many places as the flood carries a lot of silt into the flooded area thereby making that area very good for agriculture. However, if the floods are deep i.e., much, they can be harmful as they can destroy villages, etc.
Controlling floods will involve taking risks. Since floods are natural.
CAUSES OF FLOODING
1.Heavy rain.
2.Long periods of rain.
3.Very wet saturated soil.
4.Compacted or dry soil.
5.Overflowing rivers.
6.Lack of drainage system.
7.Blocked drainage.
FACTORS THAT DETERMINE OR AFFECT FLOODING
1.The amount of water that runs off the wind.
2.The amount of rainfall.
3.The temperature.
4.The type and condition of the soil.
5.The amount and type of vegetation.
CONSEQUENCES OF FLOODING
1.Loss of lives and valuable properties.
2.Destruction of crops.
3.Loss of livestock.
4.Widespread of waterborne diseases.
5.Disruption of business activities.
HOW TO CONTROL FLOODING
1.By building dams
2.By building very high walls along the rivers banks to prevent it from overflowing its banks.
3.By widening the rivers.
4.By building reservoirs to hold more water during flooding.
5.Streams may be diverted so that they do not flow into a particular river and result to flooding.
6.Irrigation
SOIL EROSION
Soil erosion is the wearing away and loss of soil from an area. Soil erosion is the washing away of soil by heavy rain or wind resulting in formation of gulley and landslides and leaving behind barren rocks and slits on which plants can no longer grow. Soil erosion poses serious to agriculture as it wash away the nutrient from the topsoil.
TYPES OF EROSION
Based on the cause of erosion, we have:
Water erosion: This is the erosion caused as a result of heavy rainfall or flood which wash away the soil on slopes. Constant flow of water create gullies over a long time. When rain falls on sloppy ground the water runs off thereby washing away a large portion soil and also breaking down rocks in a process called weathering.
CLASSIFICATION OF CROPS AND THEIR USES
Wind erosion: This the erosion caused by fast moving wind which exposes the top soil and carry them away. Wind erosion can be controlled by planting trees along the wind path. These trees serve as windbreaker
HUMAN ACTIVITIES THAT CAUSE EROSION
Burning of bush: The deliberate or accidental burning of bush destroys the soil structure and exposes it to erosion and high temperature.
Farming: The cutting of trees and clearing of farmlands exposes the soil to erosion
Building of house and industries: The clearing of land before the building of houses promote erosion.
Growth of town: Development of town leads to the exposure of the soil surfaces which can easily be washed away.
Construction of roads: The construction of new road leads to the breaking of soil structure which make it easy for soil to be washed away.
EFFECTS OF EROSION
1.It reduces soil fertility.
2.It damages road and soil surfaces.
3.It destroys farmland and farm produce.
4.It may lead to lose of buildings.
5.It leads to loss of lives through accident and building collapse.
CONTROL OF EROSION
1.Indiscriminate burning of bushes should be stopped.
2.Plant of trees and cover crops.
3.The practice of mulching in which cut grass residue are spread over the soil surface under a growing crop which retains moisture, reduces weeds and prevent exposure of the soil surface thereby reducing soil erosion.
4.Construction of terraces on sloppy land.
METHODS OF PREVENTING SOIL EROSION
1.Wind erosion can be prevented by planting cover crops, grasses and belt of trees which serves as wind breakers.
2.Water erosion and flooding can be prevented through proper canals and drainage channels to lead water away in to rivers.
3.Gully erosion can be stopped by small dams with stones and sticks along the gullies in order to capture soil that is being washed away.
4.Terrace should be build to prevent erosion. Terraces are barriers constructed along contours of the land which hinders the rapid flow of water down the slopes.
WEEK THREE: DESERTIFICATION AND DEFORESTATION
Deforestation is the continuous removal of trees without replacing or replanting them. Deforestation is also the permanent destruction of forest in order to make land available for other uses.
CAUSES OF DEFORESTATION
1.Removal of trees to make land available for the construction of roads, building of houses and industries, recreational centres and so on.
2.Indiscriminate logging by poachers for industrial purposes like the production of paper, furnitures, sculptures etc.
3.Felling of trees to make wood available for domestic purposes like cooking.
4.Burning of forest for hunting and farming.
5.Natural causes like forest fire during thunderstorm or landslides can also lead to loss of forest trees.
EFFECTS OF DEFORESTATION
1.Deforestation leads to the loss of of wildlife and biodiversity. This means that wild animals in the forest like monkeys, gorillas etc, will gradual die off.
2.Deforestation contributes to climatic change and increase in global warming.
3.Deforestation lead to the lost of habitat of so many species of animals especially birds.
4.Deforestation lead to decrease in atmospheric oxygen and increase in CO2. This means that plants and animals are in danger because there will less oxygen to breathe in.
5.Deforestation leads to flooding and erosion.
6.Deforestation may lead to starvation and homeless. This is because there will be no food or wood to build shelter.
7.Deforestation may lead to economic loss if forest raw materials are no longer available for industry to use or export.
WAYS TO CONTROL DEFORESTATION
1.Afforestation: This is the planting of trees in places where they are not planted before. Afforestation helps to bring forest condition to places where they do not exist before. An example of afforestation is the “Plant A Tree” initiative.
2.Reforestation: This is the replanting of trees to replace those trees that have been removed from the forest.
3.Government should make laws against indiscriminate poaching and logging.
4.Government should make laws against bush burning.
5.The use of forest guards to keep trespassers away from the forest.
IMPORTANCE OF FOREST
1.The forest provides raw materials like timber, latex, and medicinal extracts etc, to industries.
2.Trees of the forest help in purifying the atmosphere by removing excess CO2 from the atmosphere for photosynthesis.
3.The forest is the home of many animals which provides hides and skin for us to make clothes, bags, shoes and so on.
4.The availability of forest provides employment for a lot of people.
5.The presence of trees slows down erosion and desert encroachment.
DESERTIFICATION
A desert is a large area of land with little or no rainfall where very few plants grow. Desertification is the process of making a non desert area a desert. It is the spread of desert to places where they previously do not exist. In Nigeria, about 50% to 75% of the northeast and northwestern states are deserts. State like Bauchi, Bornu, Gombe, Taraba, Jigawa, Kano, Katsina, Kebbi, Sokoto, Yobe and Zamfara all have deserts. Like most environmental hazards, desertification is majorly influenced by climatic change and human activities.
LIST OF SOME DESERTS IN AFRICA
1.Sahara desert is the largest hot desert found in North Africa.
2.Namid desert found in Southern Africa.
3.Kalahari desert also found in Southern Africa.
CAUSES OF DESERTIFICATION
1.Overgrazing.
2.Frequent bush burning.
3.Water impoundment.
4.Deforestation.
5.Increased salinity.
6.Drought.
7.Climatic change.
WEEK FOUR: BUSH BURNING
Bush burning is the agricultural practice that involve the that involving the clearing and burning of bush. It is a common practice in west Africa. Although it is a quick way of getting rid of the weeds, it is considered a type of environmental hazard.
PRACTICES THAT INFLUENCE BUSH BURNING
1.Bush burning is done as a method of hunting.
2.Bush burning is used as a method of wedding.
3.Bush burning is used to stimulate the growth of fresh grasses during dry season.
4.The burning of refuse can influence bush burning.
5.Smoking.
6.Wind.
EFFECTS OF BUSH BURNING
1.Bush burning spreads rapidly and can destroy economic crops.
2.Bush burning exposes the soil to erosion which wash away soil nutrient.
3.When bush burning is not controlled it may lead to loss of valuable properties.
4.Bush burning and forest fire leads the destruction of wildlife.
5.Bush burning is a major source of air pollution.
6.Bush burning contributes to the depletion of the ozone layer.
7.Bush burning lead to loss of soil nutrients.
CONTROL OF BUSH BURNING
Environmental laws are made to guide against indiscriminate bush burning and anyone caught will be prosecuted. It is against the law to burn bushes.
The burning of bushes can be controlled through the following ways:
1.Establishment of agencies to control, prevent and monitor bush burning in Nigeria. Some of these agencies include; Federal Environmental protection agency (FEPA), Lagos state environmental protection agency (LASEPA), National Forest Conservation Council of Nigeria (NAFCON)
2.Ministries of environment are established to control and regulate environmental activities that may cause disaster
3.Laws are enacted by the government to control bush burning.
4.Agencies should educate the masses about the effects of bush burning.
5.Mass media should be used to enlighten people on how to control bush burning.
WEEK FIVE: DEPLETION OF THE OZONE LAYER
DESCRIPTION OF OZONE LAYER
Ozone is a pale blue poisonous gas found in the earth’s upper atmosphere. Ozone (O3) is a triatomic molecule of oxygen. It is stable than the diatomic oxygen gas (O2). It is present in low concentration in the troposphere. Ozone was first discovered by Louis Soret in 1865 and confirmed by Schonbein in 1867.
The amount of Ozone in the atmosphere is measured in Dobson’s unit.
The stratosphere (upper atmosphere) has highest concentration of ozone to form what is called the ozone layer. The ozone layer is about 10km-50km above d earth surface.
Ozone is produced in the atmosphere by the action of ultraviolet ray from the sun on oxygen.
O2 + UV —-> 2[O]
[O] + O2 —-> O3
The ozone is destroyed by free oxygen atoms or elements that react with oxygen.
O3 + [O] —-> 2O2
The depletion of ozone layer simply means the continuous reduction in the amount of ozone in the atmosphere. Substances like chlorofluorocarbons (CFC), carbon monoxide (CO), nitrogen oxides etc, are responsible for the depletion of the ozone layer.
IMPORTANCE OF OZONE LAYER
1.Ozone is very important in the preparation of pharmaceuticals and synthetic lubricants.
2.Ozone is used for bleaching substances.
3.Ozone is used to kill microorganisms in water system.
4.Ozone layer protect the earth from the heat of the sun.
5.The ozone layer shields man, animals and plants from the harmful ultraviolet rays from the sun.
INDUSTRIAL USES OF OZONE
Industrially ozone is used to:
1.disinfect laundry in hospitals and food factories.
2.deodorize air and objects especially after fire.
3.assist in processing plastics to allow adhesion of inks.
4.wash fresh fruits and vegetable to kill yeast, mould and bacteria.
5.manufacture chemical compounds.
THE HAZARDS OF DEPLETION OF OZONE LAYER TO LIFE ON LIFE
1.Exposure of the skin of man and other animals to the dangerous ultraviolet rays of the sun which can cause cancer of the skin.
2.Depletion of the ozone layer allows more ultraviolet rays to reach us which may harm aquatic plants and animals thereby disrupting the ecosystem.
3.Ozone layer depletion leads to the increase in the amount of greenhouse gases which leads to excessive warming of the earth resulting to alteration of season.
4.Depletion of ozone layer leads to global warming which contributes to flooding and other related hazards.
5.Depletion of ozone layer in the lower atmosphere may lead to increase in toxic gases.
CONTROL MEASURES AGAINST DEPLETION OF OZONE
1.There must be regulation on the use of chlorofluorocarbons (CFC).
2.There must be a reduction of bush burning.
3.There must be control of burning in household activities.
4.Elimination of chemicals responsible for the depletion of the ozone layer.
5.Reduction of poisonous gases that can interact negatively with the ozone layer.
6.Development of technology that will not emit dangerous gases from household equipments like refrigerator, air-conditioner etc.
GLOBAL WARMING
Global warming is the increase in the average temperature of the earth over a prolonged period of time.
Two of the major causes of global warming are:
1.depletion of the ozone layer
2.green house effect (increase in greenhouse gases).
Greenhouse effect is the reflection of radiant heat back to the earth as a result of accumulation of greenhouse gases (CO2, H2O CH4) in the lower atmosphere. The most important greenhouse gas is CO2. The increase in the amount of carbon dioxide in the atmosphere is a major cause of greenhouse effect and global warming.
Sources of carbon dioxide in the atmosphere include:
- burning of fossil fuels like coal, petrol, kerosene etc.
- release of carbon dioxide from the exhaust of vehicles.
- release of carbon dioxide from factories.
- increase in the population of man also contributes to the high percentage of carbon dioxide.
- deforestation.
- bush burning.
- urbanization.
CONSEQUENCES OF GLOBAL WARMING
1.Seasonal/climate change.
2.Rising oceans.
3.Increase in flooding occurrences.
4.Melting ice caps or polar ice.
5.Increase in average temperature of the world.
CONTROL OF GLOBAL WARMING
Global warming can be control through the following activities.
1.Planting of trees will purify the atmosphere by absorbing carbon dioxide for photosynthesis and releasing oxygen which contributes to the formation of ozone layer.
2.Reduction in bush and waste burning.
3.Recycling of waste materials.
4.Use of alternative energy sources other than fossil fuels e.g. solar power, wind turbine, water turbine.
5.Electric vehicles should be used to reduce emission of carbon dioxide.
WEEK SIX: RESOURCES FROM LIVING THINGS ELESSON NOTES
Natural resources are valuable material that is found in nature and used by people to meet their needs. Some natural resources are air, water, plants and animals, metals soil and so on.
Resources are either renewable or non renewable.
Renewable resources are resources that are naturally replaced after use. Plants and animals are renewable resources because they can reproduce.
Non-renewable resources are resources that are not replaced after use. All mineral resources are non renewable.
Resources from living things include the resources from plants and animals.
RESOURCES FROM PLANTS
Resources gotten from plants include:
1.food crops.
2.cash crops.
3.medicinal plants.
4.textile materials.
5.wood materials.
6.manure and yeast.
FOOD CROPS
These are crops cultivated only to feed man. They include the following.
1.Leafy vegetables (like bitter leaf, pumpkin, spinach) which provides us with minerals (like calcium and iron) and vitamins.
2.Fruits (like orange, mango, pineapple etc) provide the body with essential vitamins and mineral salts.
3.Grains and cereals (like rice, oat, millet, sorghum etc) which are rich in starch, oil and protein.
4.Staples and tubers (like yam, cassava, potato etc) which are essentially rich in starch.
5.Oil plants (like oil palm, groundnut, coconut etc) from which we get oil. The oil is used domestically, for cooking.
CASH CROPS
These are crops cultivated by the farmer for sale and to make profit. They include:
1.Fibre crops (like cotton, milkweed etc) are used in textile industries for making clothes. It is also used in making pulp for papers.
2.Oil crops (like groundnut, oil palm, Shea-butter, coconut etc) sold to earn income.
3.Beverage crops (like cocoa, coffee, tea etc) are also exported.
4.Latex crops (like rubber, Arabic gum, raffia palm) used for making latex and exported.
MEDICINAL PLANTS
The bark leaves and roots of some plants are used for medicinal purposes. Examples include Dongoyaro, lemon grass, kolanut trees, tobacco etc.
TEXTILE CROPS
These are crops used in the manufacturing of clothes, dyes and other accessories. They are mainly fibrecrops like cotton and dyeplants like indigo plant.
WOODS
These are products from trees mainly used for building, furnitures, cooking etc. Examples of plants that provide us with wood include Mahogany, ebony, obeche, African walnut etc.
ORNAMENTAL PLANTS
These are plants that are used for beautifying the environment. Examples include: hisbiscus plant, Rose plant, Pride of Barbados etc.
COMPOST AND MANURE
When plants die or when their leaves fall to the ground, they decompose and add to the nutrient of the soil. Legumes also add to soil fertility when they are planted
RESOURCES FROM ANIMALS
Animals are reared by man to provide food and other essential resources. These resources include:
1.Food: Livestocks are reared to provide food in form of meat for man. Man obtain nutritional values like proteins, fat, vitamins and mineral salts from meat. E.g pork from pigs, chevon from goat, mutton from sheep, poultry meat, fish, prawn etc.
2.Eggs: Eggs laid by poultry birds are also important sources of protein. The fowls that are reared mainly for the production of eggs are called layers. Examples of poultry include: chicken, Turkey, duck etc.
3.Dairy products: Dairy deals with the production milk from livestocks especially cattle. Dairy products include milk, cheese, yoghurt etc.
4.Bones: Bones are the part of the body found within animals. Bones are used in the production of glues and ornamental decoration.
5.Horns: Horns are extension of the skull of some animals. Horns are used fir producing cattle, sheep, goat etc
6.Feathers: Feathers are coverings on the body of birds. Feathers are used for decoration.
7.Hide and skin: Hide from large animals and skin from small animals are used for making belts, bags, drums, purses. Hide and skin are gotten from goats, sheep, horse, camel, cattle etc.
8.Beast of burden: These are animals used for carrying loads and doing farm work. These animals include horses, donkey, camel, cows etc.
9.Animal dungs: Animal waste are used to produce manure which add to soil fertility and increase crop yield.
ECONOMIC IMPORTANCE OF RESOURCES FROM LIVING THINGS
1.They serve as source of food to man e.g beans, cassava, beans, cow, goat etc.
2.They serve as raw materials for industries e.g Timber, tannin and hides for leather, milk etc.
3.They provide drugs and antidotes.
4.Plants make oxygen available for us and purify our environment.
5.Animals are used for farming activities.
6.Ornamental plants are used to decorate our environment.
7.Animals that are used as pets helps to fight loneliness.
8.They are sources of income generation for farmers.
9.They provide employment for the people.
10.Animals in zoos and parks serve as centre for tourism.
WEEK SEVEN: RESOURCES FROM NONLIVING THINGS (SOLID MINERALS)
MINERAL RESOURCES
Mineral resources are resources deposited in the earth crust for the benefit of man. A mineral can exist as a single element or as a compound. It could also be deposited in a solid or liquid state. Often, solid minerals are deposited in the earth as ore. An ore is a compound of a useful element that is found deposited in the earth.
Some mineral resources, their location and their uses in Nigeria are given below
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GENERAL IMPORTANCE OF MINERAL RESOURCE
1.It serve as a source of income for the state and country.
2.They are raw materials for industries.
3.They are required construction of roads e.g. bitumen.
4.They are used as source of fuel. E.g. coal.
5.It brings about provision of employment and income for individuals.
6.The availability of mineral resources makes life easier and more comfortable.
7.The presence of mineral resources in a country brings fame to the country.
WEEK EIGHT: LIGHT ENERGY ELESSON NOTES
Light can be defined as a form of energy which produces electromagnetic radiation capable of causing visual sensation. Light is a kind of electromagnetic wave (waves that can travel in vacuum). Light is the fastest substance known to man. Light travels at a speed of 3×108 m/s (300,000,000 metres per second or 299,792.5 km/s). Light travels in a straight line in what is called Rectilinear propagation of light until it encounters an obstacle. When light cannot pass through an object, shadow is formed. An object that does not allow light to pass through it is an opaque object while those objects that allow light to pass through them are called transparent object.
An object that can produce light on it’s own is called luminous e.g. sun, light bulb, fire. While an object that does not produce light but may reflect it is called non luminous e.g. the moon, mirror, stone, chair etc.
Light waves are also called light rays. A line with an arrowhead is used to represent a ray of light. A collection of light rays is called light beam.
There are there type of beam. They are:
1.Parallel beam: This is the type of beam in which the light rays are parallel to one another.
2.Divergent beam: This is the type of beam in which the ray scatters from a point which is usually the source, a convex mirror or a concave lens.
3.Convergent beam: This is the type of beam in which the rays converge or meet at a point called focus.
PROPERTIES OF LIGHT
Light has the following properties:
1.Reflection.
2.Refraction.
3.Diffraction.
4.Dispersion.
5.Interference.
6.Polarization.
REFLECTION OF LIGHT
Reflection of light is the change in the direction of light after dashing against a surfray. Reflection involves two rays of light: an incoming incident ray and an outgoing reflected ray.
LAW OF REFLECTION
1.The angle of incident ray, the normal and reflected ray at the point of incidence all lie on the same plane.
2.The angle of incidence (i) and the angle of reflection (r) are equal but on opposite sides of the normal. i = r
N.B: The normal is an imaginary line at right angle to the mirror at the point of incidence.
TYPES OF REFLECTION
1.Regular or specular reflection: This is when parallel beam of light is reflected in one direction. Such reflection takes place on smooth, polished surface such as a plane mirror.
2.Diffuse reflection: This is when a parallel beam of light is reflected in different directions. Such reflection takes place from a rough surface, such as water surface or paper surface.
REFRACTION
Refraction is the bending or change in the direction of wave when it moves from one medium to another where its speed is different. A medium is a material or space that allows wave pass through it. Refraction is responsible for image formation by lens and the eye.
When you dip your legs into a pool, it disappears bent in the pool. A fish in an aquarium seem to radically change position as it is being viewed from different view points. These are as a result of refraction.
LAWS OF REFRACTION
1.The first law of refraction states that the incident ray, the refracted ray and the normal at the point of incidence all lie on the same plane.
2.The second law states that the sine of the angle of incidence (i) to the sine of the angle of refraction (r) is a constant for a given pair of media.
This is also known as Snell’s law and the ratio of “I” to “r” is called the refractive index.
LENSES AND GLASS PRISMS
Lenses are curved glasses that disperse or coverge light to a focus.
There are two main types of lenses:
1.Concave lens (diverging lens): This is a lens that bulges outward. A concave lens diverges or scatters light. It is used to correct shortsightedness (myopia)
2.Convex lens (converging lens): This lens bends inward. It converges light to a real focus. It is used to correct longsightedness (hypermetropia).
There are also two types of glass prisms:
(i) Rectangular glass prisms (ii) Triangular glass prisms
VISION
Vision is the ability to create an image. The organ of the body that is concerned with vision is the eye. Light enters through a clear covering of the eye called the cornea. It then passes through the adjustable opening in the iris called the pupil. Beyond the pupil is the lens which is a bit soft and flexible. The lens focus image on the retina while like a film or screen at the back of the eye.
The eye and camera are alike in function and arrangement of part. Both are compared for a lot of reasons.
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DISPERSION OF LIGHT
This is the splitting or separation of light into different colours. Each colour bends by different degrees when refracted. The colours of light that are gotten after separation are called spectrum. Dispersion of light can be done by passing light through a triangular prism.
RAINBOW
A natural phenomenon that demonstrates the dispersion of light is the the formation of rainbow. The rainbow is an arc of light with an angular radius of 42° centred on a direction which is opposite to that of the sun in sky (I.e it is centered on the direction of propagation of the sun rays). Thus, if the sun low in the sky (I.e close to the horizon) we see almost a full circle. If the sun is higher up in the sky we see a smaller arc. If the sun is more than the angular radius 42° above the horizon, then there will be no rainbow (for viewers on ear surface).
Observers on a hill may see part of the rainbow below the horizontal i.e an arc greater than a semicircle. Passengers on airplane can sometimes see a full circle. The colours of the rainbow vary smoothly from red on the outside and violet on the inside. There are seven colours of the rainbow; red, orange, yellow, green, blue, indigo and violet.
In the dispersion of light, a ray of enters into a triangular glass prism and it is dispersed into colours seven colours written as ROYGBIV.
WEEK NINE: SOUND ENERGY
Sound is a wave caused by vibration of matter. It is a property of vibrating objects. These objects may be solid, liquid or gases. If there is an elastic medium (i.e a medium which is capable of being compressed between the vibrating object and a suitable apparatus such as a microphone, ear of animals) noise or sound will be detected.
Sound may be produced in a variety of ways, normally as a result of some mechanical disturbances on an object, causing it to vibrate.
For example:
- A blow by a hammer on a piece of iron causes the iron (and the hammer) to vibrate for a short while.
- A guitar string vibrates under the rubbing action of the bow.
- A tightly stretched skin on a drum is set to vibrate when it is struck.
- Vocal cord of humans vibrate when air from the lungs pass out through the larynx
- An explosion sets the surrounding air into vibration.
TRANSMISSION OF SOUND
This is the passage of sound from one point to another e.g. from one room in a building to another or from the street into a room in the building.
The transmission and production of sound can be demonstrated in the laboratory using a tuning fork. The tuning fork has two steel prongs which when struck with a hard surface gives sound. During the vibration, the prongs of the tuning fork present a hazy appearance due to their rapid to and fro movements. If the vibrating prongsare dipped into a beaker of water, the water is seen to be violently agitated. The transmission of natural vibration from the tuning fork to the water is called Resonance.
Sound is transmitted through matter such as air, water or solid metals. The matter or material through which sound is transmitted is called a medium. Sound travels faster in solid than in liquid and faster in liquid than in gases. The speed of sound in dry air is 332 m/s, 1484 m/s in water and 5,120 m/s in iron.
REFLECTION OF SOUND
When sound reflects off a special curved surface called a parabola, it will bounce out in a straight line no matter where it originally hits.
Many entertainment stages are designed as a parabola so that the sound will go directly into the audience instead of bouncing on the stage. If the parabola is closed off by another curve surface it is called an ellipse. Sound will travel from one focus to another no matter where it strikes the wall.
A whispering gallery is designed as an ellipse. If your friend stands at one focus and you stand at the other, his whisper will be heard clearly by you. No one in the rest of the room will hear anything. Reflection of sound is responsible for echoes.
An echo is a sound that is reflected back to it source. While multiple overlapping echoes is called reverberation.
HEARING
Hearing is the ability to perceive sound by detecting vibrations, change in the pressure of the surrounding medium through an organ called the ear. The inability of the ear to hear is called deafness. There are three main components of the ear: the outer ear, the middle ear and the inner ear.
The outer ear includes the visible part of the ear (or the pinna), the auditory canal and the eardrum. Sound travel in waves and when these waves arrive at the eardrum they cause vibration. The eardrum amplifies the incoming air pressure waves to a single firm with a certain extent (amplitude): this allows fir the differentiation of sound.
The middle ear consists of a smaller air-filled chamber that is located behind the eardrum. Within the chamber are three smallest bones in the body known collectively as ossicles. The ossicles are; malleus (hammer), incus (anvil) and stapes (stirrup). The stapes is the smallest bone in the body. The ossicles aid the transmission and amplification of the vibration from the ear drum to the inner ear.
The inner ear, which comprises the cochlea (a coiled canal filled with fluid) which is connected to auditory nerve cells which pass on the signal to the brain.
WEEK TEN: MAGNETISM
A magnet is a substance or materal that attracts metals like iron and other ferometals. Magnetism is the ability of a substance to attract a metal that contains iron.
LODESTONE
Lodestones are rock that are magnetic. They are made of magnetite (Fe3O4) a form of iron oxide. A piece if iron is then referred to as a lodestone. The Chinese appear to have been the first to discover the lodestone. These qualities of lodestone led to its use as an early form of compass by Chinese sailors. This is because when the stone is magnetized it will be attracted to the earth’s magnetic field pole. Also, when it is suspended in the air it slowly turns and points towards the pole.
LAWS OF MAGNETISM
When a bar magnet is suspended so that it can freely rotate and then freely come to rest. It is noticed that it remains in a North-South direction. Also, when the pole of another bar magnet is brought near the north pole of the suspended bar magnet, the magnet would not attract each other, that is, they repel. But when the north pole of the bar magnet is brought towards the south pole of the suspended bar magnet, they would attract each other.
Therefore, in each case, when like poles are brought near each other there is repulsion. When unlike poles are near each other there is attraction. These led to the laws of magnetism which states that:
“Like poles repel each other while unlike poles attract each other”. E.g. north-north or south-south will repel while south-north or north-south will attract.
MAGNETIC POLE AND MAGNETIC FIELD
To identity magnetic poles, a magnet can be brought near a magnet whose poles have already been Identified (a standard magnet). If attraction occurs, it means that the pole of the magnet beside the identified pole of the standard magnet is not alike e.g. North pole of the standard magnet will be attracted to the south pole of the other magnet and vice versa. If repulsion occurs, it means both poles are alike and by this the unknown poles of the magnet are consequently identified.
MAGNETIC FIELD
This is a condition found in the region around a magnet, characterized by the existence of magnetic poles. It can also be described as the region or space around a magnet in which magnetic force is felt.
THE CARE OF MAGNETS
There is the need to care for magnets so that they would not lose their ability to magnetise. The following ways are necessary for caring for magnets.
1.Magnets should be heaped with like-magnets. They should be kept away from the edge of flexible magnets because it can actually reverse the polarity.
2.Replacement covers can be purchased for many of the polar power magnets because magnet covers and materials may eventually be worn and torn
3.They should be clean by wiping them gently with a damp soapy sponge and should not be immersed in water.
4.They should be stored by spreading magnetic signs flay on a smooth metal surface.
5.They should not be left in hot weather or brought close to fire as it can destroy their properties.
