Light and Sound In this unit:1) Properties of light2) Reflection3) Colours4) Refraction5) Properties of sound6) Hearing
Part 1 – Properties of Light Light travels in straight lines: Laser
Light travels VERY FAST – around 300,000 kilometres per second.At this speed it cango around the world 8times in one second.
Light travels much faster than sound. For example: 1) 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.
We see things because they reflect light into our eyes: Homework
Luminous and non-luminous objects A luminous object is one that produces light.A non-luminous object is one that reflects light. Luminous objects Reflectors
ShadowsShadows are places where light is “blocked”: Rays of light
Properties of Light summary1) Light travels in straight lines2) Light travels much faster than sound3) We see things because they reflect light into our eyes4) Shadows are formed when light is blocked by an object
Part 2 - Reflection Reflection from a mirror: NormalIncident ray Reflected ray Angle of Angle of incidence reflection Mirror
The Law of Reflection Angle of incidence = Angle of reflectionIn other words, light gets reflected from a surface at____ _____ angle it hits it. The same !!!
Clear vs. Diffuse ReflectionSmooth, shiny surfaces have a clear reflection:Rough, dull surfaces havea diffuse reflection.Diffuse reflection is whenlight is scattered indifferent directions
Using mirrorsTwo examples: 2) A car headlight 1) A periscope
ColourWhite light is not a single colour; it is made up of a mixture of the seven colours of the rainbow.We can demonstrate this bysplitting white light with aprism:This is how rainbows areformed: sunlight is “split up”by raindrops.
The colours of the rainbow: Red Orange Yellow Green Blue Indigo Violet
Adding colours White 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 Adding blue andmakes magenta green makes cyan(purple) (light blue)Adding red Adding alland green three makesmakes yellow white again
Seeing colourThe colour an object appears depends on the colours of light it reflects.For example, a red book only reflects red light: White Only red light light is reflected
A pair of purple trousers would reflect purple light(and red and blue, as purple is made up of red and blue): Purple light A white hat would reflect all seven colours: White light
Using coloured lightIf we look at a coloured object in coloured light we see something different. For example, consider a football kit: Shirt looks red White light Shorts look blue
In different colours of light this kit would look different: Red Shirt looks red light Shorts look black Shirt looks black Blue light Shorts look blue
Some further examples: Colour object Object Colour of light seems to be Red Red Red socks Blue Black Green Black Red Black Blue teddy Blue Green RedGreen camel Blue Green RedMagenta book Blue Green
Using filtersFilters can be used to “block” out different colours of light: Red Filter Magenta Filter
Investigating filtersColour of filter Colours that could be “seen” Red Green Blue Cyan Magenta Yellow
RefractionRefraction is when waves ____ __ or slow down due totravelling in a different _________. A medium issomething that waves will travel through. When a pen isplaced in water it looks like this:In this case the light rays are slowed down by the waterand are _____, causing the pen to look odd. The twomediums in this example are ______ and _______. Words – speed up, water, air, bent
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
Drawing sounds…This sound wave has a_____ frequency:This sound wave has a___ _frequency:
Drawing sounds…This sound wave has a_____ amplitude(loud):This sound wave has a_____ amplitude(quiet):
Hearing problemsOur hearing range can be damaged by several things:1) Too much ear wax!2) Damage to the auditory nerve3) Illness or infections4) Old age (not like Mr Richards)
Other sound effects…Like light, sound can be…1) Reflected – sound reflections are called ______.2) Refracted – this is why you might sound strange if you try talking underwater
The EarLabel 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 turnvibrations into an electrical signalThis part connects the ear to the mouthThis part “channels” the sound towards the ear drum