light and colours
Post on 08-Apr-2018
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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 andgalaxiesgive outlight.
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 forma string ofshining beads
to attractinsects.
tail of worm
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Some cold things give out light:
some fungi glow worms
light sticks
LEDs glow-in-the-darkstickers
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How do we see light sources?
Light travels from asource to our eyes.
We can see sources ina dark room.
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Can we see in the dark? If there is no light
we cannot see anything!
Lets 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 thatthe babysquirrelwatches as
it feeds?
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ReflectionWhen 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 andcan be seen on the wall.
wall
mirror
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Move the mirror
The light reaches a differentplace on the wall.
wall
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Look in a mirror Light is reflected.
You can see a reflection.
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Changethedirectionof thelight
beam Light is still reflected. You see a reflection
- in a differentdirection.
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Multiple
reflections The lamp hangs
between two large
mirrors onopposite walls.
The reflection inthe first mirror is
reflected in thesecond mirror,which is reflectedagain in the firstmirror - - -
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Now for
somegames!
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Colour
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Rainbow
red
orange
yellowgreen
blue
indigo
violet
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Colours
White light is made upof lots of colours
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Colours from white light
Look at a lampthrough the grating.
You will seecolours.
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red
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blue
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Adding colourswith 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 +R
ed 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 beamsof 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
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