LIGHT

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LIGHT !

• from bonfires to lasers

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Sources of light
A bonfire

• Hot objects give out light.

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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!
• 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 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
mirror

• Light is reflected as a beam and can be seen on
  the wall.

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Move the mirror
wall

• The light reaches a different place on the 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

• red
• orange
• yellow
• green
• blue
• indigo
• violet

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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
spiral

• 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.

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Laser show

• Physics is in everything