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 !!!
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: R O Y G. B I V 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 uniform: Shirt looks red White light Shorts look blue
In different colours of light this uniform would look different: Red Shirt looks red light Shorts look black Shirt looks black Blue light Shorts look blue
Some further examples: Colour objectObject Colour of light seems to be Red RedRed socks Blue Black Green Black Red BlackBlue 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 ruleris placed in water it looks like this:In this case the light rays are slowed down by the waterand are _____, causing the ruler to look odd. The twomediums in this example are ______ and _______.
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):
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
Hearing TestsHow old are you?https://www.youtube.com/watch?v=AXhRmv1mrsHearing testhttps://www.youtube.com/watch?v=h5l4Rt4Ol7M