light & optics: making a telescope dr lisa jardine-wright

Light & Optics: Making a Telescope

Dr Lisa Jardine-Wright

How do astronomers make discoveries?

Telescopes with lensesConverging Lens

Convergent rays

f

Experiment 1

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

MirrorLens (15)Pin-holeLamp

About 15cm

Metre Rule

Experiment 1

MirrorLens (15)Pin-holeLamp

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

Fobject

F image

Experiment 2a

Graph Paper Screen (shows image)

Lens (15)Lamp Cork (object)

More than the focal length of

your lens

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 object

F

image

Experiment 2b

Graph Paper Screen (shows image)

Lens (15)Lamp Cork (object)

Less than the focal length of

your lens

Move the screen can you find a

focussed image of the cork

Experiment 2b

Lens (15)Cork (object)

Less than the focal length of

your lens

Take screen away and move the

lamp to the side.

Lamp Graph Paper Screen (shows image)

Telescope Experiment

Graph Paper Screen (shows image)

Lens (15)Lamp Cork (object)

Lens (30)

10cm

Refracting Telescopes

Lens 1 Lens 2Object

Image 1

Image 2

F1 F1 F2 F2

Refracting Telescopes

Lens 1 Lens 2Object

Image 1

Image 2

F1 F1 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

Light is blocked…

in some wavelengths but not others.

How do we “see” things?

Light is blocked…

in some wavelengths but not others.

How do we “see” things?

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