A Virtual Tour of the Universe

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Light Optics Making a Telescope
Dr Lisa Jardine-Wright
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How do astronomers make discoveries?
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Telescopes with lenses

• Converging Lens

Convergent rays
f
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Experiment 1

• Move the lens until you see a bright dot next to
  the pin hole that is in focus.
• Write down the distance of the lens from the
  pin-hole the focal length

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Experiment 1
Mirror
Lens (15)
Pin-hole
Lamp
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Investigating Lenses

• Draw ray diagrams to investigate what happens as
  you move an object to the lens that its focus.
  And further away than the focus.

lens
F
image
object
F
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Experiment 2a
Graph Paper Screen (shows image)
Cork (object)
Lens (15)
Lamp
Move the screen until you see a focussed image of
the cork
More than the focal length of your lens
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Investigating Lenses

• Draw ray diagrams to investigate what happens as
  you move an object to the lens that its focus.
  And further away than the focus.

lens
F
image
object
F
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Experiment 2b
Graph Paper Screen (shows image)
Cork (object)
Lamp
Lens (15)
Move the screen can you find a focussed image of
the cork
Less than the focal length of your lens
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Experiment 2b
Graph Paper Screen (shows image)
Cork (object)
Lamp
Lens (15)
Take screen away and move the lamp to the side.
Less than the focal length of your lens
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Telescope Experiment
Graph Paper Screen (shows image)
Cork (object)
Lamp
Lens (15)
Lens (30)
10cm
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Refracting Telescopes
Lens 2
Object
Lens 1
Image 1
F1
F1
F2
F2
Image 2
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Refracting Telescopes
Lens 2
Object
Lens 1
Image 1
F1
F1
F2
Image 2
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Reflecting Telescopes
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How do we make a picture?
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How do we make an picture?
Green
Red
Blue
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Light

• Visible light is just one tiny part of a much
  bigger range of waves called
• Electromagnetic Spectrum

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Electromagnetic Spectrum
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Visible Spectrum
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Infra-red
Visible
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How do we see things?
Light is blocked in some wavelengths but not
others.
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How do we see things?
Light is blocked in some wavelengths but not
others.
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http//coolcosmos.ipac.caltech.edu/image_galleries
/ir_zoo/
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The SunVisible
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The SunRadio
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The SunMicrowave
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The SunInfrared
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The SunVisible
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The SunUltraviolet
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The SunX-ray
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The SunGamma Rays
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The Light from an object can tell us .

• What it looks like - Its SHAPE COLOUR
• How far away it is its DISTANCE
• And EVEN!
• What it is made of its CHEMISTRY

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