2Light and Sound In this unit: Properties of light Reflection Colours RefractionProperties of soundHearing
3Part 1 – Properties of Light Light travels in straight lines:Laser
4Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.
5Light 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.
6We see things because they reflect light into our eyes: Homework
7Luminous and non-luminous objects A luminous object is one that produces light.A non-luminous object is one that reflects light.Luminous objectsReflectors
8ShadowsShadows are places where light is “blocked”:Rays of light
9Properties of Light summary Light 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
10Part 2 - Reflection Reflection from a mirror: Mirror Normal Incident rayReflected rayAngle of incidenceAngle of reflectionMirror
11Angle of incidence = Angle of reflection The Law of ReflectionAngle of incidence = Angle of reflectionIn other words, light gets reflected from a surface at ____ _____ angle it hits it.The same !!!
12Clear vs. Diffuse Reflection Smooth, shiny surfaces have a clear reflection:Rough, dull surfaces have a diffuse reflection.Diffuse reflection is when light is scattered in different directions
13Using mirrorsTwo examples:2) A car headlight1) A periscope
14ColourWhite 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.
15The colours of the rainbow: RedOrangeYellowGreenBlueIndigoViolet
16Adding 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
17Only red light is reflected Seeing 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
18A white hat would reflect all seven colours: A 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
19Using 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
20In different colours of light this kit would look different: RedlightShirt looks redShorts look blackShirt looks blackBluelightShorts look blue
21Some further examples: ObjectColour of lightColour object seems to beRed socksRedBlueBlackGreenBlue teddyGreen camelMagenta bookHomework
22Using filters Red Filter Filters can be used to “block” out different colours of light:Red FilterMagenta Filter
23Investigating filters Colour of filterColours that could be “seen”RedGreenBlueCyanMagentaYellow
25Words – speed up, water, air, bent RefractionRefraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks like this:In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______.Words – speed up, water, air, bent
28Words – slowly, low, high, quickly Sound – The basicsWe hear things when they vibrate.If something vibrates with a high frequency (vibrates very ______) we say it has a _____ pitch.If something vibrates with a low frequency (vibrates ______) we say it has a ____ pitch.The lowest frequency I could hear was…Words – slowly, low, high, quickly
29Drawing sounds… This sound wave has a _____ frequency:
30Drawing sounds… This sound wave has a _____ amplitude (loud): This sound wave has a _____ amplitude (quiet):
31Hearing problems Our hearing range can be damaged by several things: Too much ear wax!Damage to the auditory nerveIllness or infectionsOld age (not like Mr Richards)
32Other sound effects… Like light, sound can be… Reflected – sound reflections are called ______.Refracted – this is why you might sound strange if you try talking underwater
33The Ear Label your diagram with the following: These bones are vibrated by the eardrumThis tube carries the sound towards the eardrumThis part is used to help us keep our balanceThis part “picks up” the vibrationsThis part of the ear contains many small hairs with turn vibrations into an electrical signalThis part connects the ear to the mouthThis part “channels” the sound towards the ear drum