Please enable JavaScript.
Coggle requires JavaScript to display documents.
Energy transmission through water - Light - Coggle Diagram
Energy transmission through water - Light
Introduction
A key question that divers always want to know before they dive is: “What’s the
visibility (the viz) like?” In other words: How far could they see in the water? Knowing water’s visibility is important for divers. If one can see far in the water, there
is increased splendour and increased enjoyment.
Light as a type of energy
Light is a type of energy that is radiated by the sun. Light energy is a combination of two changes: Changing electrical impulses which move in the form of waves. Changing magnetic fields in the form of magnetic waves around the
electrical impulses.
Visible light
Light visible to humans is only part of all the energy emitted from the Sun. The light which the human eye can see is made up of different coloured
light that is emitted at different wavelengths: violet; indigo, blue; green; yellow; orange and red (the rainbow colours), with red being the longest wavelength and violet being the shortest wavelength.
All the light entering the eye is reflected off objects in the line of sight. We call this
light reflection. The colour of the object being perceived is dependent upon the wavelength of the light being reflected from that object. This is ‘picked up’ by the eye and messages of what the eye sees are sent to the brain.
Transfer of light through seawater
Forms of light transmission
penetration
scattering
absorption
attenuation
refraction
Light penetration
is the measure of how deep light can travel into a medium such as a liquid or air.
Light scattering
Sediment or organic matter in the water column reduces the penetrability of
light and hence the visibility through the water. Such suspended particles either
reflect light away or scatter the light (light scattering) and so reduces the depth to
which the light can penetrate.
Light absorption
depends on the depth of the water. In shallow water, all the visible
colours of the electromagnetic spectrum can be seen. However, visible light is not
transmitted equally through water. As light goes deeper, it begins to be absorbed.
Transmission depends upon the wavelength of the light. Red, orange and yellow
light disappear first because these colours have longer wavelengths. None of these
wavelengths reaches a depth of 10 metres. Only the green to violet wavelengths
Light attenuation
the loss of light intensity as the distance through a medium
increases. Sunglasses attenuate sunlight passing through the lenses.
Light refraction
what happens to light when it
passes from one medium to another.