2 Light travels in straight lines: 21/04/2017Properties of LightLight travels in straight lines:Laser
3 Light travels VERY FAST – around 300,000 kilometres per second. 21/04/2017Light travels VERY FAST – around 300,000 kilometres per second.At this speed it can go around the world 8 times in one second.
4 Light travels much faster than sound. For example: 21/04/2017Light travels much faster than sound. For example:Thunder and lightning start at the same time, but we will see the lightning first.2) When a starting pistol is fired we see the smoke first and then hear the bang.
5 Shadows Shadows are places where light is “blocked”: Rays of light 21/04/2017ShadowsShadows are places where light is “blocked”:Rays of light
6 Quiz Which travels more quickly, light or sound? 21/04/2017QuizWhich travels more quickly, light or sound?True or false. Light can bend round corners.What causes shadows to form?Would a cup or a glass give a darker shadow?Are your shadows larger in the middle of the day or in the evening?
7 21/04/2017Copy and complete …OPAQUE objects absorb the light, don’t let it pass through. This causes a _________. E.g. a _______ is opaque.____________ objects absorb some of the light but some can still pass through. This causes a pale shadow. E.g. a china ________ is translucent.TRANSPARENT objects absorb no light letting it all pass through. This prevents a solid shadow from forming. E.g. a _________ is transparent.shadow, translucent, glass, cup, rock.
8 We see things because they reflect light into our eyes: 21/04/2017We see things because they reflect light into our eyes:Homework
9 Luminous and non-luminous objects 21/04/2017Luminous and non-luminous objectsA luminous object is one that produces light.A non-luminous object is one that reflects light.Luminous objectsReflectors
10 Properties of Light summary 21/04/2017Properties of Light summaryLight travels in straight linesLight travels much faster than soundWe see things because they reflect light into our eyesShadows are formed when light is blocked by an object
11 Reflection Reflection from a mirror: Mirror Normal Angle of incidence 21/04/2017Reflection from a mirror:NormalIncident rayReflected rayAngle of incidenceAngle of reflectionMirror
12 Angle of incidence = Angle of reflection 21/04/2017The Law of ReflectionAngle of incidence = Angle of reflectionIn other words, light gets reflected from a surface at ____ _____ angle it hits it.The same !!!
13 Clear vs. Diffuse Reflection 21/04/2017Clear vs. Diffuse ReflectionSmooth, shiny surfaces have a clear reflection:Rough, dull surfaces have a diffuse reflection.Diffuse reflection is when light is scattered in different directions
14 Using mirrors Two examples: 2) A car headlight 1) A periscope 21/04/2017Using mirrorsTwo examples:2) A car headlight1) A periscope
15 21/04/2017Pin Hole CamerasA pinhole camera is a simple device for recording an image. It uses two screens separated by a tube or box one of which is sensitive to light and one of which has a pin hole.The light passes in through the tiny hole and hits the back screen.The image you see is inverted (upside down).Using your knowledge of light try and explain why.
16 21/04/2017Pin hole camerasAs the light from the top of the tree passes through the hole it travels in a straight line to the bottom of the screen.This results in the final image recorded on the light sensitive paper being upside down. You just need to turn the paper the other way up to view it!As the light from the bottom of the tree travels in a straight line through the hole it then travels up to the top of the screen.
17 Images from pinhole cameras 21/04/2017Images from pinhole cameras
18 Copy and complete the following 21/04/2017Copy and complete the followingLight travels in ___________ lines at 300,000km/s. When it hits an opaque object it causes ___________ to be formed.When light hits a plane mirror it is ___________. The angle of ________ equals the angle of ___________.When light hits an uneven surface it is ____________.
19 Unjumble the following words 21/04/2017Unjumble the following wordsnfleecirtotefniorcarlmornaGnela fo cidinetnEalpn romirrsniufifdotmpcesruReflectionRefractionNormalAngle of incidentPlane mirrorDiffusionSpectrum
20 21/04/2017Pin hole camerasDraw a diagram of a pin hole camera and using labels explain how it works to record an image.Are they as good as a normal camera?Why?
21 SLR Cameras (digital and film) 21/04/2017SLR Cameras (digital and film)Now complete worksheet 8Kb7
22 Refraction through a glass block: 21/04/2017Wave slows down and bends towards the normal due to entering a more dense mediumWave slows down but is not bent, due to entering along the normalWave speeds up and bends away from the normal due to entering a less dense medium
23 Words – speed up, water, air, bent, medium 21/04/2017RefractionRefraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pencil is placed in water it looks like this:In this case the light rays are slowed down by the water and are _____, causing the pencil to look odd. The two mediums in this example are ______ and _______.Words – speed up, water, air, bent, medium
24 Lenses Lenses are used to focus light or disperse light 21/04/2017LensesLenses are used to focus light or disperse lightThis changes the direction that the light was travelling.There are two types of lensesDiverging – spreads light rays outConverging – focuses light rays together
25 Converging Lenses Converging lenses are convex in shape Light rays 21/04/2017Converging LensesConverging lenses are convex in shapeLight rayscoming in arefocussed by the lensFocal point
26 Diverging lenses Light rays coming in are Light rays spread out 21/04/2017Diverging lensesLight rayscoming in aredispersed by the lensLight rays spread out
27 21/04/2017Lenses and refractionIt is easier to understand what is going on with a lens if you think of it in small pieces.Each time the light is being REFRACTED through a piece of lens and so is changing speed. This causes the light to bend and change direction.
28 towards, focal point, dense, diverging, converging, away, refracted 21/04/2017LensesWhen light travels through a lens it is ________. The medium of the lens is more ______ than air so the light bends _______ the normal in the lens then _____ from the normal when it moves back into air.With a convex or ________ lens the result focuses the light to a _____ _____. The amount of curve on the lens changes the focal length.With a concave or ________ lens the result spreads out the rays of light.towards, focal point, dense, diverging, converging, away, refracted
29 Colour21/04/2017White light is not a single colour; it is made up of a mixture of the seven colours of the rainbow.We can demonstrate this by splitting white light with a prism:This is how rainbows are formed: sunlight is “split up” by raindrops.
30 The colours of the spectrum: 21/04/2017RedOrangeYellowGreenBlueIndigoViolet
31 Video on colour YouTube - Sci Eye Colour Video on light YouTube - Scientific Eye Light & ReflectionBoth good but both 20 minutes each. Don’t use them back to back!
32 21/04/2017Questions on the videoExplain fully why the sky is blue and the sun appears yellow.List the primary colours.What do colour filters do to white light?Explain why a red t-shirt looks red in white light.Explain why a red t-shirt looks black in green light.Video 138 colour and refraction
34 21/04/2017Adding coloursWhite light can be split up to make separate colours. These colours can be added together again.The primary colours of light are red, blue and green:Adding blue and red makes magenta (purple)Adding blue and green makes cyan (light blue)Adding red and green makes yellowAdding all three makes white again
35 Only red light is reflected 21/04/2017Seeing colourThe colour an object appears depends on the colours of light it reflects.For example, a red book only reflects red light:HomeworkWhitelightOnly red light is reflected
36 A white hat would reflect all seven colours: 21/04/2017A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue):Purple lightA white hat would reflect all seven colours:Whitelight
37 21/04/2017Using coloured lightIf we look at a coloured object in coloured light we see something different. For example, consider a football kit:Shirt looks redWhitelightShorts look blue
38 In different colours of light this kit would look different: 21/04/2017In different colours of light this kit would look different:RedlightShirt looks redShorts look blackShirt looks blackBluelightShorts look blue
39 Some further examples: 21/04/2017ObjectColour of lightColour object seems to beRed socksRedBlueBlackGreenBlue teddyGreen camelMagenta bookHomework
40 Using filters Red Filter 21/04/2017Using filtersFilters can be used to “block” out different colours of light:Red FilterMagenta Filter
41 Investigating filters 21/04/2017Investigating filtersColour of filterColours that could be “seen”RedGreenBlueCyanMagentaYellow
42 Red Blue Green White Yellow Cyan Magenta 21/04/2017RedBlueGreenWhiteYellowCyanMagenta