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Sun and Air

  NO HEATING INVOLVED - all non toxic.

You will need:
  • Transparent plastic tray ( eg sandwich box) 20 x 10 x 3cm minimum
  • Small bright torch ( bike light is ideal)
  • inside of toilet roll ( or kitchen roll)
  • Milk ( 20 ml )
  • Dropper
  • 1 sheet of kitchen roll
  • Elastic band to go round toilet roll
  • An old CD ( remember them?)

Try this first 

  • Can you use the torch to produce an image like the one shown here?
  • What does this demonstration show about the nature of white light? 

 What we did..

  1. put your torch inside the cardboard tube.
  2. cover the end with a sheet of kitchen roll . This is to avoid you dazzling yourself
  3. set up your torch so that you can view it through the tray of water
  4. carefully add milk drop by drop and view the torch light and note its colour.
  5. after a few drops you will see the colour of your torch change 
  6. try to take photographs to show this effect

 The tekkie bit..

This experiment helps to explain why we sometimes see orange and red colours at sunset and sunrise.

As the sun sets - its rays need to pass through a greater distance of the atmosphere. 

The atmosphere contains water vapour and other gases. These scatter the blue light more than the other colours in white light.

When there is a lot of atmosphere to travel through, the blue is scattered even more - but the red and orange carry on and so the sun appears to change colour. This short video explains it well:

image by Georgie
 

Comments 5

David Fowkes on Wednesday, 29 April 2020 19:47

Hi Guys, Just to say that it would help to have a couple of clothes pegs and a pen ( or pencil ) handy tomorrow. Also it works better if the room is slightly darkened. The tray I used is 23 x 16 x 7 cm deep. In many ways the bigger the better but we need it to be transparent. Ordinary tap water is fine for this one.
See you tomorrow.

Hi Guys, Just to say that it would help to have a couple of clothes pegs and a pen ( or pencil ) handy tomorrow. Also it works better if the room is slightly darkened. The tray I used is 23 x 16 x 7 cm deep. In many ways the bigger the better but we need it to be transparent. Ordinary tap water is fine for this one. See you tomorrow.
Guest - Helen Rashbrook on Thursday, 30 April 2020 11:40

Hi dave see you soon

Hi dave see you soon
magnus miller on Thursday, 30 April 2020 12:48

Dave. Is soya milk alright for the experiment?

Dave. Is soya milk alright for the experiment?
magnus miller on Thursday, 30 April 2020 12:52

We have a 20x20x10cm box. Is that also alright?

We have a 20x20x10cm box. Is that also alright?
David Fowkes on Thursday, 30 April 2020 13:54

Hi yes and yes - both should work fine.
D

Hi yes and yes - both should work fine. D
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Friday, 30 October 2020

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