Embed Size (px)
Citation preview
Welcome BackWelcome Back
Term 3 and Term 4Term 3 and Term 4
Administrative StuffAdministrative Stuff
Hand up Science Holiday Assignment Hand up Science Holiday Assignment now or the next time I will see younow or the next time I will see you
Hand up Science File now or the next Hand up Science File now or the next time I will see youtime I will see you
Textbook Volume 2Textbook Volume 2 But don’t throw away your Volume 1 But don’t throw away your Volume 1
because you will still need to learn the 2 because you will still need to learn the 2 chapters in Volume 1 for final year examschapters in Volume 1 for final year exams
Chapters that will be Chapters that will be covered in Term 3covered in Term 3
Light and ColourLight and Colour Introducing ElectricityIntroducing Electricity Household ElectricityHousehold Electricity Force and PressureForce and Pressure
Chapters that will be Chapters that will be covered in Term 4covered in Term 4
Forces at WorkForces at Work
Light and ColourLight and Colour
State the speed of lightState the speed of light Define luminous and non luminous objectDefine luminous and non luminous object State that light travels in a straight lineState that light travels in a straight line Angle of incidence = angle of reflectionAngle of incidence = angle of reflection Distinguished between regular and diffused Distinguished between regular and diffused
lightlight Define reflectionDefine reflection State characteristics of image in a plane mirrorState characteristics of image in a plane mirror State the uses of plane and curved mirrorState the uses of plane and curved mirror
Light and ColourLight and Colour
Define refraction and its effectsDefine refraction and its effects Describe the dispersion of white light by Describe the dispersion of white light by
prismprism Describe how rainbow is formedDescribe how rainbow is formed
Introducing ElectricityIntroducing Electricity
To draw and circuit diagram with variety of To draw and circuit diagram with variety of electrical componentelectrical component
Explain the meaning of current, voltage, Explain the meaning of current, voltage, resistance and to state their unitsresistance and to state their units
Recognize the resistance of circuit can be Recognize the resistance of circuit can be varied by arranging resistors in series and in varied by arranging resistors in series and in parallelparallel
Explain how heating, magnetic and chemical Explain how heating, magnetic and chemical will affects of an electric current and its will affects of an electric current and its applicationsapplications
Importance of electricityImportance of electricity
Household ElectricityHousehold Electricity
Explain what is meant by power and its unitExplain what is meant by power and its unit Solve problems in the cost of using electrical Solve problems in the cost of using electrical
appliancesappliances Discuss on reducing electrical energy wasteDiscuss on reducing electrical energy waste State electrical hazards and precautionary State electrical hazards and precautionary
measuresmeasures To appreciate the need of Singapore which has To appreciate the need of Singapore which has
no natural resources of her own to conserve no natural resources of her own to conserve energyenergy
Force and PressureForce and Pressure
Define force as push or pullDefine force as push or pull List different types of forcesList different types of forces Effects of forcesEffects of forces Newton as the unit of forceNewton as the unit of force Define pressureDefine pressure Application pressureApplication pressure Simple calculations in pressureSimple calculations in pressure
Do worksheet on the Do worksheet on the introduction of light introduction of light and colourand colourUnscramble the wordsUnscramble the words
E3: Light and E3: Light and ColourColourTextbook pg 34 Textbook pg 34
ObjectivesObjectives
At the end of this lesson you should be At the end of this lesson you should be able to:able to: State the speed of lightState the speed of light Define luminous and non-luminous objectsDefine luminous and non-luminous objects Give examples of luminous and non-Give examples of luminous and non-
luminous objectsluminous objects
Introduction to Introduction to LightLightShort videoclipShort videoclip
Speed of lightSpeed of light
Light travels at about 300000 kilometres Light travels at about 300000 kilometres per secondper second
Takes about 8 minutes to reach EarthTakes about 8 minutes to reach Earth Light travel faster than soundLight travel faster than sound
Calculating SpeedCalculating Speed
Can you remember the formula?Can you remember the formula? Speed = Distance/TimeSpeed = Distance/Time
Try inquiry time pg 35 Try inquiry time pg 35 (10 minutes)(10 minutes)
All the questionsAll the questions
What is light?What is light?
Form of energyForm of energy Enable us to see things around usEnable us to see things around us Use by plants to make foodUse by plants to make food
How does light travel?How does light travel?
Light travels in straight Light travels in straight lineslines
Watch short clip on how Watch short clip on how light travel.light travel.
How does light travel?How does light travel?
Light travels in straight Light travels in straight lineslines
Watch short clip on how Watch short clip on how light travel.light travel.
Thin line of light is Thin line of light is called raycalled ray
A stream of light is A stream of light is called a beamcalled a beam
What are the sources of What are the sources of light?light?
Luminous objectLuminous object SunSun StarsStars LampsLamps FiresFires
What are the sources of What are the sources of light?light?
Most objects are non-Most objects are non-luminousluminous MoonMoon BookBook HouseHouse TreesTrees
Show animationShow animation
On luminous and non-luminous objectsOn luminous and non-luminous objects
SummarySummary
Calculations on speed Calculations on speed of lightof light
Understand what is lightUnderstand what is light Differentiate between Differentiate between
luminous and non-luminous and non-luminous objects and luminous objects and give examplesgive examples
How light travelHow light travel
Check Point (page 36)Check Point (page 36)
Luminous objects are Luminous objects are objects that produce light objects that produce light and non-luminous objects and non-luminous objects do not give out light. E.g. do not give out light. E.g. sun (luminous), moon sun (luminous), moon (non-luminous)(non-luminous)
LightLight Straight lineStraight line
Do Theory Workbook pg Do Theory Workbook pg 19-2019-20
All questions now.All questions now.
Why are we able to see Why are we able to see ourselves in a mirror?ourselves in a mirror?
Look at the mirror – our Look at the mirror – our imageimage
Image formed when Image formed when light rays bounce off the light rays bounce off the mirror and travel into mirror and travel into our eyesour eyes
This bouncing of light This bouncing of light off mirror is called off mirror is called reflection (definition)reflection (definition)
Why are we able to see Why are we able to see ourselves in a mirror?ourselves in a mirror?
Ray of light that strikes a surface = incident rayRay of light that strikes a surface = incident ray Ray of light that reflected by a surface = reflected rayRay of light that reflected by a surface = reflected ray At the point where the incident ray strikes the surface, At the point where the incident ray strikes the surface,
line is perpendicular to the surface = normalline is perpendicular to the surface = normal
Why are we able to see Why are we able to see ourselves in a mirror?ourselves in a mirror?
The normal divides the angle between the incident ray and The normal divides the angle between the incident ray and reflected rayreflected ray
Angle of incidence = angle between the incident ray and the Angle of incidence = angle between the incident ray and the normalnormal
Angle of reflected = angle between the reflected ray and the Angle of reflected = angle between the reflected ray and the normalnormal
Angle of incidence = Angle of reflection (Law of reflection)Angle of incidence = Angle of reflection (Law of reflection)
Characteristics of an image Characteristics of an image formed by plane mirrorformed by plane mirror
Image is at the same distance from Image is at the same distance from the plane mirror as the objectthe plane mirror as the object
Image uprightImage upright Image same sizeImage same size Image formed is virtual image Image formed is virtual image
(image located behind the mirror (image located behind the mirror where light does not actually pass)where light does not actually pass)
Laterally invertedLaterally inverted
Types of reflectionTypes of reflection
Regular reflectionRegular reflection Diffuse reflectionDiffuse reflection
Regular ReflectionRegular Reflection
Parallel beam of light hit a smooth Parallel beam of light hit a smooth surface such as plane mirrorsurface such as plane mirror
Reflected as parallel beamReflected as parallel beam Image is very clearImage is very clear
Regular ReflectionRegular Reflection
Surfaces such as mirrors, polished Surfaces such as mirrors, polished metal, calm surface of watermetal, calm surface of water
Diffused ReflectionDiffused Reflection
Reflection off rough surfacesReflection off rough surfaces Beam strike a rough surface, the Beam strike a rough surface, the
rays are reflected in many directionsrays are reflected in many directions
Diffused ReflectionDiffused Reflection
No images or no clear images are No images or no clear images are formedformed
Surfaces such as frosted glass, Surfaces such as frosted glass, rough paper and clothrough paper and cloth
Do Inquiry Time pg 39 & Do Inquiry Time pg 39 & Checkpoint pg 40Checkpoint pg 40
InquiryInquiry Window: regular reflectionWindow: regular reflection White cloud: diffused reflectionWhite cloud: diffused reflection Regular reflection: mirror, shiny metal surfaceRegular reflection: mirror, shiny metal surface Diffused reflection: white board, rough glassDiffused reflection: white board, rough glass
CheckpointCheckpoint The bouncing of light off the mirror is called The bouncing of light off the mirror is called
reflectionreflection Angle of incidence is equal to angle of Angle of incidence is equal to angle of
reflectionreflection Regular and diffused reflection. Regular: from Regular and diffused reflection. Regular: from
smooth surface, Diffused: from rough smooth surface, Diffused: from rough surfacessurfaces
Today’s ObjectivesToday’s Objectives
At the end of this lesson, you will be At the end of this lesson, you will be able to:able to: Draw the ray diagram (plane mirror)Draw the ray diagram (plane mirror) State the uses of plane mirrorsState the uses of plane mirrors State the uses of curved mirrorsState the uses of curved mirrors
Ray DiagramsRay Diagrams
WorksheetWorksheet
What are the steps?What are the steps?
Draw the image of the objectDraw the image of the object Object distance is equal to image distanceObject distance is equal to image distance
Pick one extreme on the image of the Pick one extreme on the image of the object and draw the reflected ray which object and draw the reflected ray which will travel to the eye as it sights at this will travel to the eye as it sights at this point. point. Draw a bold line for the reflected ray (from the Draw a bold line for the reflected ray (from the
mirror to the eye) and a dashed line as an mirror to the eye) and a dashed line as an extension of this reflected ray; the dashed line extension of this reflected ray; the dashed line extends behind the mirror to the location of extends behind the mirror to the location of the image point the image point
What are the steps?What are the steps?
Draw the incident ray for light Draw the incident ray for light traveling from the corresponding traveling from the corresponding extreme on the object to the mirror extreme on the object to the mirror
Repeat steps 2 and 3 for all other Repeat steps 2 and 3 for all other extremities on the object.extremities on the object.
Uses of plane mirrorsUses of plane mirrors
Rear view mirrorRear view mirror Help driver to see traffic behind the carHelp driver to see traffic behind the car
Mirror on the wallMirror on the wall Makes the room look biggerMakes the room look bigger
MicroscopesMicroscopes Periscope (see pg 41)Periscope (see pg 41)
Use in a submarineUse in a submarine
Types of curved mirrorsTypes of curved mirrors
ConvexConvex ConcaveConcave Image formed from these types of Image formed from these types of
mirror is different from those formed mirror is different from those formed by plane mirrorsby plane mirrors
Convex MirrorsConvex Mirrors
Form upright images Form upright images that are smaller than that are smaller than the objectthe object
Large field of view Large field of view (allow many things to (allow many things to be seen)be seen)
Uses are:Uses are: Security cameraSecurity camera Blind corners of roadsBlind corners of roads Rear view mirrors in Rear view mirrors in
vehiclesvehicles
Concave MirrorsConcave Mirrors
Form upright magnified Form upright magnified images if the object is images if the object is close to the mirrorclose to the mirror
If object is further If object is further away, the image is away, the image is invertedinverted
Uses are:Uses are: Reflect light into the Reflect light into the
microscopemicroscope Dentist’s mirror to Dentist’s mirror to
magnifies image of teethmagnifies image of teeth Car headlightsCar headlights
Do checkpoint pg 43Do checkpoint pg 43
Image is uprightImage is upright Image same size as objectImage same size as object Image is the same distance as the object Image is the same distance as the object
from the mirrorfrom the mirror Image is laterally invertedImage is laterally inverted The rear view mirrorThe rear view mirror To make the room look biggerTo make the room look bigger Concave (dentist mirror) and convex (for Concave (dentist mirror) and convex (for
blind corners of roads)blind corners of roads)
Do summary worksheetDo summary worksheet
NowNow
Do theory workbook pg Do theory workbook pg 21-2321-23
Qn 1-3 (pg 21)Qn 1-3 (pg 21) Qn 4a, 5 (pg 22)Qn 4a, 5 (pg 22) Qn 6 (pg 23)Qn 6 (pg 23)
Today’s ObjectivesToday’s Objectives
At the end of this lesson, you will be At the end of this lesson, you will be able to:able to: Define refractionDefine refraction State the effects of refractionState the effects of refraction
What is refraction?What is refraction?
Light changes direction when it travels Light changes direction when it travels from one transparent material into from one transparent material into anotheranother
Eg. From air into water, from water into Eg. From air into water, from water into glass, and also from glass into airglass, and also from glass into air
Refraction of light is the bending of light Refraction of light is the bending of light as it changes its speed when it passes as it changes its speed when it passes from one transparent medium to anotherfrom one transparent medium to another (definition)(definition)
RefractionRefraction
When a ray of light enters a medium When a ray of light enters a medium at an angle, the speed of light will at an angle, the speed of light will change. This change in the speed change. This change in the speed of light is the cause of the bending of of light is the cause of the bending of light or the change in the direction of light or the change in the direction of light. light.
Refractionnormal
normal
a
d
bc
glass
air
Light bends away from normal as it leaves the glass and enters the air.
Light bends towards the normal when it travels from air to glass.
Refracted ray
Reflected ray
Emergent ray
Incident light ray
What happen in the What happen in the diagram?diagram?
From air to glass,From air to glass, light entering a denser medium since light entering a denser medium since
air is less dense than glass block.air is less dense than glass block. Speed of light Speed of light decreasesdecreases..
From glass to air,From glass to air, Light entering a less dense medium.Light entering a less dense medium. Speed of light Speed of light increasesincreases..
What happen in the What happen in the diagram?diagram?
Speed of light in:Speed of light in: air/ vacuumair/ vacuum :: 3 x 103 x 1088 m/s (very m/s (very
fast)fast) waterwater :: 2.26 x 102.26 x 1088 m/s m/s
(fast)(fast) glassglass :: 1.97 x 101.97 x 1088 m/s m/s
(slow)(slow)
Behaviour of light moving to Behaviour of light moving to and from different mediumsand from different mediums
Less dense to Less dense to denser (Air to denser (Air to glass)glass)
Speed of light Speed of light decreasesdecreases
Bend towards Bend towards normalnormal
Behaviour of light moving to Behaviour of light moving to and from different mediumsand from different mediums
Denser to less Denser to less dense (glass to air)dense (glass to air)
Speed of light Speed of light increasesincreases
Bend away from Bend away from normalnormal
Some images of Some images of refractionrefraction
Some images of Some images of refractionrefraction
Application of RefractionApplication of Refraction
Magnifying glassMagnifying glass SpectaclesSpectacles MicroscopesMicroscopes TelescopesTelescopes Overhead Overhead
projectorsprojectors
Effects of RefractionEffects of Refraction
Cause swimming pool Cause swimming pool to appear shallowerto appear shallower
Cause straw to Cause straw to appear bend towards appear bend towards the surface of the the surface of the waterwater
Causes the letters to Causes the letters to appear nearer to the appear nearer to the surface of the glass surface of the glass than they actually arethan they actually are
Reflection vs RefractionReflection vs Refraction
ReflectionReflection Incident angle=reflected Incident angle=reflected
angleangle Incident ray and Incident ray and
reflected ray travel in reflected ray travel in the same mediumthe same medium
Incident and reflected Incident and reflected ray travel with the same ray travel with the same speedspeed
RefractionRefraction Incident angle not equal Incident angle not equal
to refracted angleto refracted angle Incident and refracted Incident and refracted
ray travel in different ray travel in different mediummedium
Incident and refracted Incident and refracted ray travel at different ray travel at different speedspeed
Do Checkpoint pg 44Do Checkpoint pg 44
All questionsAll questions
Today’s ObjectivesToday’s Objectives
At the end of this lesson, you will be At the end of this lesson, you will be able to:able to: Describe how the white light dispersed Describe how the white light dispersed
by prismby prism Describe how rainbow is formedDescribe how rainbow is formed
Light dispersionLight dispersion
Is also called white lightIs also called white light Mixture of different coloursMixture of different colours Separate the colours using a prismSeparate the colours using a prism When white light travels through a When white light travels through a
glass prism, refraction causes the glass prism, refraction causes the light to splitlight to split
The different colour of light travel at The different colour of light travel at different speed into the prism thus it different speed into the prism thus it get separatedget separated
Spectrum of white lightSpectrum of white light Splitting of white light = dispersionSplitting of white light = dispersion
Spectrum of LightSpectrum of Light
Consists of Consists of RedRed OrangeOrange YellowYellow GreenGreen BlueBlue IndigoIndigo VioletViolet
How to remember the colours? ROY G BIVHow to remember the colours? ROY G BIV
How rainbow is formed?How rainbow is formed?
When white light travels through When white light travels through water droplets in the airwater droplets in the air
Spectrum of white light disperses Spectrum of white light disperses into its seven coloursinto its seven colours
Rainbow is formed (usually after Rainbow is formed (usually after rainy days)rainy days)
How to combine the How to combine the colours of the spectrum?colours of the spectrum?
By using a second prismBy using a second prism See pg 46See pg 46
How do we see colours?How do we see colours?
We see colours that are reflectedWe see colours that are reflected Some lights are absorbed and some are Some lights are absorbed and some are
reflectedreflected Leaves are green because it reflected Leaves are green because it reflected
green colour and absorb the rest of the green colour and absorb the rest of the colourscolours
Objects appear white, because it reflected Objects appear white, because it reflected all colours and absorb noneall colours and absorb none
Objects appear black, because that Objects appear black, because that absorb all colours and no light is reflectedabsorb all colours and no light is reflected
Depends on what colour light is reflected Depends on what colour light is reflected into our eyes.into our eyes.
How do we see colours?How do we see colours?
White light
red green
White light
No light is reflected,is black
White light
The primary colour The primary colour lightslights
When Red, Green and blue lights are When Red, Green and blue lights are mixed:mixed:
Red +green=yellowRed +green=yellow Blue+green=cyanBlue+green=cyan Red+blue=magentaRed+blue=magenta Red+green+blue=whiteRed+green+blue=white
What happens when red What happens when red light is shone onto alight is shone onto a
White object:White object:red
The white object reflects any colour lights
When white light falls on When white light falls on a a
Black object:Black object:
Black object absorbs all coloured lights.
When red light falls on aWhen red light falls on a
Green object:Green object:
black
The green object absorbs all colour lights except green
When blue light falls on a When blue light falls on a ::
Red object :Red object :black
The red object absorbs all colour light except red.
Do checkpoint pg 48Do checkpoint pg 48
All questionsAll questions
