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LIGHT !from bonfires to lasers
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Sources of light
Hot objects give out light.
A bonfire
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The Sun Sunset in Venice
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Stars
Stars and galaxies give out light.
Picture: Liverpool Telescope
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Lightning
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A worm living in dark caves sends out light from its tail.
Liquid droplets form a string of shining beads to attract insects.
tail of worm
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Some cold things give out light:
some fungi glow worms light sticks LEDs ‘glow-in-the-dark’
stickers
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How do we see light sources?
Light travels from a source to our eyes.
We can see sources in a dark room.
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Can we see in the dark?
If there is no light we cannot see anything!
Let’s try a test– Put a few small objects into the black
bag-----
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How do we see things that are not sources of light?
Light bounces off and some reaches our eyes.
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On the look out ! How do you
know that the baby squirrel watches as it feeds?
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Reflection
When light bounces off something we say the light is reflected.
We can try this with rough surfaces and shiny surfaces.
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Shiny surfaces
Light is reflected as a beam and can be seen on the wall.
wall
mirror
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Move the mirror
The light reaches a different place on the wall.
wall
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Look in a mirror Light is reflected.
You can see a reflection.
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Change the direction of the light beam Light is still reflected.
You see a reflection - in a different
direction.
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Multiple reflections The lamp hangs
between two large mirrors on opposite walls.
The reflection in the first mirror is reflected in the second mirror, which is reflected again in the first mirror - - -
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Now for some games !
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Colour
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Sunlight shining on CDs Where do the
colours come from?
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Rainbow
redorang
eyellow green blue indigoviolet
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Colours
White light is made up of lots of colours
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Colours from white light Look at a lamp
through the grating.
You will see colours.
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red
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blue
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Adding colours with light
This is different to adding paints
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Red + Blue magenta
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Blue + Green cyan
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Green + Red yellow
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yellow
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magenta
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cyan
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Fairy lights
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Uses
Lasers- produce very bright beams of light.The atoms all give out their light
together
CDs use laser light and reflection-
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CDs
The surface has tiny pits and smooth bits in a spiral pattern
the pits scatter light from a laser the smooth bits reflect the light so a coded message is read.
spiral
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Laser show
Physics is in everything