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Author Topic: Shadows!! Why are they differently toned??  (Read 2224 times)

Offline Seany

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Shadows!! Why are they differently toned??
« on: 09/06/2007 13:01:01 »
There are different shades of shadows! Some are darker than others. Some our quite light coloured!! But all the same, they are all grey-black!!

Why are they differently toned?

If an object blocks the light from a light source, shouldn't the shadow be PITCH black, so that if you put a little object behind that blocking object, you cannot see the little object, as there is no light?

I hope someone understands this!

I also thought that light could still go around the object and into the shadow.. But light goes straight? Or maybe the light is reflected from somewhere else..


 

Offline lightarrow

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Shadows!! Why are they differently toned??
« Reply #1 on: 09/06/2007 19:19:38 »
There are different shades of shadows! Some are darker than others. Some our quite light coloured!! But all the same, they are all grey-black!!
Why are they differently toned?
If an object blocks the light from a light source, shouldn't the shadow be PITCH black, so that if you put a little object behind that blocking object, you cannot see the little object, as there is no light?
I hope someone understands this!
I also thought that light could still go around the object and into the shadow.. But light goes straight? Or maybe the light is reflected from somewhere else..

What you say is a very interesting effect. It's cited in the first page of the book "Mechanics Acoustics and Thermology" R.W. POHL (first edition 1930). It's cited because it proves, with the "Coloured Shadows" effect, that colours are not physical properties of matter. Infact, switching on a light source, we can notice that a shadow become colored, even if the light from that source doesn't go in the area of that shadow!

This is the experiment:
you should have two light source of different colours, for example a yellowish bulb lamp and a bluish neon lamp, located in different places. You have an object and, with the bulb lamp only switched on, you draw the contour of its shadow on the table. Then you switch off the bulb and switch on the neon lamp. Nothing strange happens but look at the area you have previously drawn and then switch on the bulb lamp.

Since the light from the bulb lamp does not go in that area, nothing happens now, physically. But, magically, the shadow is blue now!

It's an optical illusion (not very easy to explain: brain makes a sort of chromatic subtraction).
« Last Edit: 09/06/2007 19:22:17 by lightarrow »
 

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Shadows!! Why are they differently toned??
« Reply #1 on: 09/06/2007 19:19:38 »

 

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