Light and sound
Transcript of Light and sound
![Page 1: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/1.jpg)
Light and SoundLight and Sound
In this unit:
1) Properties of light2) Reflection3) Colours4) Refraction5) Properties of sound6) Hearing
![Page 2: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/2.jpg)
Part 1 – Properties of Part 1 – Properties of LightLight
Light travels in straight lines:
Laser
![Page 3: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/3.jpg)
Light travels VERY FAST – around 300,000 kilometres per second.
At this speed it can go around the world 8 times in one second.
![Page 4: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/4.jpg)
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.
![Page 5: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/5.jpg)
We see things because they reflect light into our eyes:
Homework
![Page 6: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/6.jpg)
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
![Page 7: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/7.jpg)
Shadows
Shadows are places where light is “blocked”:
Rays of light
![Page 8: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/8.jpg)
Properties of Light Properties of Light summarysummary
1) 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
![Page 9: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/9.jpg)
Part 2 - ReflectionPart 2 - ReflectionReflection from a mirror:
Incident ray
Normal
Reflected ray
Angle of incidence
Angle of reflection
Mirror
![Page 10: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/10.jpg)
The Law of ReflectionThe Law of Reflection
Angle of incidence = Angle of Angle of incidence = Angle of reflectionreflection
In other words, light gets reflected from a surface at ____ _____ angle it hits it.
The same !
!!
![Page 11: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/11.jpg)
ColourColour
White 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.
![Page 12: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/12.jpg)
The colours of the rainbow:The colours of the rainbow:
R O Y G. B I V RedOrangeYellowGreen
BlueIndigoViolet
![Page 13: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/13.jpg)
Adding coloursAdding 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 all three makes white again
Adding red and green makes yellow
![Page 14: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/14.jpg)
Seeing colourSeeing colourThe colour an object appears depends on the
colours of light it reflects.
For example, a red book only reflects red light:
White
light
Only red light is
reflected
![Page 15: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/15.jpg)
A 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 light
White
light
![Page 16: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/16.jpg)
Using coloured lightUsing coloured light
If we look at a coloured object in coloured light we see something different. For example, consider a football uniform:
White
light
Shorts look blue
Shirt looks red
![Page 17: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/17.jpg)
In different colours of light this uniform would look different:
Red
lightShirt looks red
Shorts look black
Blue
light
Shirt looks black
Shorts look blue
![Page 18: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/18.jpg)
Some further examples:
Object Colour of lightColour object seems to be
Red socks
Red Red
Blue Black
Green Black
Blue teddy
Red Black
Blue
Green
Green camel
Red
Blue
Green
Magenta book
Red
Blue
Green
![Page 19: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/19.jpg)
Using filtersUsing filtersFilters can be used to “block” out different colours of
light:
Red Filte
r
Magenta
Filter
![Page 20: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/20.jpg)
Investigating filtersInvestigating filters
Colour of filter Colours that could be “seen”
Red
Green
Blue
Cyan
Magenta
Yellow
![Page 21: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/21.jpg)
RefractionRefractionRefraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a ruler is placed in water it looks like this:
In this case the light rays are slowed down by the water and are _____, causing the ruler to look odd. The two mediums in this example are ______ and _______.
Words – speed up, water, air, bent
![Page 22: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/22.jpg)
![Page 23: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/23.jpg)
Sound – The basicsSound – The basics
We 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
![Page 24: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/24.jpg)
Drawing sounds…Drawing sounds…
This sound wave has a _____ frequency:
This sound wave has a ___ _frequency:
![Page 25: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/25.jpg)
Drawing sounds…Drawing sounds…
This sound wave has a _____ amplitude (loud):
This sound wave has a _____ amplitude (quiet):
![Page 26: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/26.jpg)
Other sound effects…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
![Page 27: Light and sound](https://reader034.fdocuments.in/reader034/viewer/2022042614/55873c27d8b42a7b098b4582/html5/thumbnails/27.jpg)
Hearing TestsHearing Tests
How old are you? https://www.youtube.com/watch?v=AXhRmv1mrs4
Hearing testhttps://www.youtube.com/watch?v=h5l4Rt4Ol7M