ChrisKavanaugh
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HINT: Water acts as a lens bending light. Think of the british magician who performed marvels of camouflage and deception in WW2, making entire harbours disappear.
Survival Quiz Part two
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Ok everyone no one got it this time so heres the answer:
Gillnets dyed a muddy red colour are more effective than an undyed white net. this it due to the light filtering effect of suspended particles of decaying plant matter in river water and contrast as explained below:
Pure water absorbs most red and orange light, less yellow still less green and relatively little blue light and thus appears blue.
Inshore waters however are stained by the yellow products of vegetables decay.
These substances are very persistant and have the property of absorbing
much blue light, less green and very little yellow or red. These yellow substances act as such strong filters as to over-ride the blue filtering properties of pure water this results in the water appearing reddish-brown when viewed from beneath in fresh water lakes and rivers. If the yellow stain is rather more diluted the red and yellow light is absorbed by the water and the blue by the yellow substances and this leaves green as the colour least absorbed. This is the explanation for the green colour of the water around our coast. This colour filter action of a water mass is chiefly responsible for the fact that colours appear different below the surface in river water.
Contrast underwater:
A distant object under water is usually detected because it is either a little darker or little brighter than the background it is seen against. Contrasts are low under water because much the image forming light from an object is either scattered out of the light path or absorbed by the water before it reaches the eye, whilst daylight is scattered out of it's downward path into the eye thus interposing a veil of brightness between the object and the eye. Obviously if the rate of contrast decrease remains the same, the distance that an object can recede before it becomes invisible depends on the original contrast with the water background.
Sorry for the long explanation but in short:
if you open you eyes underwater in a river the water looks muddy red because the water is full of particals of decaying plants whos yellow colour filters out the blue green and yellow light, so a muddy red colour net is camouflaged against the muddy red water and as contrast is reduced by water as explaind above it makes it almost invisible :-D
I'll put another question up on monday
is anyone Enjoying this quiz if not say and i'll stop
Gillnets dyed a muddy red colour are more effective than an undyed white net. this it due to the light filtering effect of suspended particles of decaying plant matter in river water and contrast as explained below:
Pure water absorbs most red and orange light, less yellow still less green and relatively little blue light and thus appears blue.
Inshore waters however are stained by the yellow products of vegetables decay.
These substances are very persistant and have the property of absorbing
much blue light, less green and very little yellow or red. These yellow substances act as such strong filters as to over-ride the blue filtering properties of pure water this results in the water appearing reddish-brown when viewed from beneath in fresh water lakes and rivers. If the yellow stain is rather more diluted the red and yellow light is absorbed by the water and the blue by the yellow substances and this leaves green as the colour least absorbed. This is the explanation for the green colour of the water around our coast. This colour filter action of a water mass is chiefly responsible for the fact that colours appear different below the surface in river water.
Contrast underwater:
A distant object under water is usually detected because it is either a little darker or little brighter than the background it is seen against. Contrasts are low under water because much the image forming light from an object is either scattered out of the light path or absorbed by the water before it reaches the eye, whilst daylight is scattered out of it's downward path into the eye thus interposing a veil of brightness between the object and the eye. Obviously if the rate of contrast decrease remains the same, the distance that an object can recede before it becomes invisible depends on the original contrast with the water background.
Sorry for the long explanation but in short:
if you open you eyes underwater in a river the water looks muddy red because the water is full of particals of decaying plants whos yellow colour filters out the blue green and yellow light, so a muddy red colour net is camouflaged against the muddy red water and as contrast is reduced by water as explaind above it makes it almost invisible :-D
I'll put another question up on monday
is anyone Enjoying this quiz if not say and i'll stop
