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Properties of Light in Water

Properties of Light in Water. Refraction Attenuation with depth Light and Trophic Status Secchi Disk Application. Light Penetration & Attenuation. (I o ). Euphotic zone. Note refraction. 1% I o. Amount reflected depends on wave conditions and ice cover.

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Properties of Light in Water

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  1. Properties of Light in Water Refraction Attenuation with depth Light and Trophic Status Secchi Disk Application

  2. Light Penetration & Attenuation (Io) Euphotic zone Note refraction 1% Io Amount reflected depends on wave conditions and ice cover. Light that penetrates the surface may then be absorbed, reflected or transmitted. Light intensity decreases logarithmically with depth; a process called attenuation (extinction).

  3. Refraction: • A fish in water looks bigger and closer than it really is due to bending of light toward the surface as it leaves the water to your eye. PSYCH!

  4. Attenuation (or extinction) coefficient (k is defined as: k = (ln Io – lnIz) / z Light intensity at a given depth can be calculated as: Iz = Ioe-kz • Different wavelengths of light absorb differently in pure water. Blues and greens penetrate deepest and reds the least. Why the “deep blue sea”? • Particles and colored dissolved organic matter will further influence how quickly different colors of light are absorbed in natural waters.

  5. ( = 100% 1- I1 – I2 I1 (

  6. Secchi Depth and Trophic Status Secchi depth (ZSD) can be used to estimate the attenuation coefficient (k). k= 1.7 / ZSD ; This translates into the 1% light level being 2.7 times ZSD, or that 16% of surface irradiance remains at the ZSD. (k)

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