Light and colours

8/7/2019 Light and colours

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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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Light and colours