Light & Optics:
Making a Telescope
Dr Lisa Jardine-Wright
How do astronomers make discoveries?
Telescopes with lenses
Converging Lens
Convergent rays
f
Experiment 1
Lamp Pin-hole
About
15cm
Lens (15)
Mirror
Metre
Rule
1. Move the lens until you see a bright dot next
to the pin hole that is in focus.
2. Write down the distance of the lens from the
pin-hole = the focal length
Experiment 1
Lamp Pin-hole
Lens (15)
Mirror
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
object
F
image
Experiment 2a
Lamp
Cork
(object)
Lens (15)
More than the
focal length of
your lens
Graph Paper Screen
(shows image)
Move the screen
until you see a
focussed image
of the cork
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 F object
Experiment 2b
Lamp
Cork
Lens (15)
(object)
Less than the
focal length of
your lens
Graph Paper Screen
(shows image)
Move the screen
can you find a
focussed image
of the cork
Experiment 2b
Lamp
Cork
Lens (15)
(object)
Less than the
focal length of
your lens
Graph Paper Screen
(shows image)
Take screen away
and move the
lamp to the side.
Telescope Experiment
Lamp
Cork
(object)
Lens (15)
Graph Paper
Lens (30)
Screen
(shows image)
10cm
Refracting Telescopes
Lens 2
Object Lens 1
Image 1
F1
F1 F2
Image 2
F2
Refracting Telescopes
Lens 2
Object Lens 1
Image 1
F1
F1
Image 2
F2
Reflecting Telescopes
How do we make a picture?
How do we make an picture?
Red
Green
Blue
“Light”
Visible light is just one tiny part of a much bigger
range of waves called:
Electromagnetic Spectrum
Electromagnetic Spectrum
Visible Spectrum
Infra-red
Visible
How do we “see” things?
Light is blocked…
in some
wavelengths but not
others.
How do we “see” things?
Light is blocked…
in some
wavelengths but not
others.
http://coolcosmos.ipac.caltech.edu/image_galleries/ir_zoo/
The Sun:
Visible
The Sun:
Radio
The Sun:
Microwave
The Sun:
Infrared
The Sun:
Visible
The Sun:
Ultraviolet
The Sun:
X-ray
The Sun:
Gamma
Rays
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