1. Measurement of Absorption in Seawater
Kenneth Voss
3/30, KJV, Optics Seminar

2. Introduction
Light beam is attenuated (c), this attenuation is by scattering (b) and absorption (a).

3. Pure water Transmission = P/Po C T(1m) T(0.25m) .01 0.99 0.997
Introduction
Pure water
Transmission = P/Po
C T(1m) T(0.25m)

4. Introduction

5. Introduction

6. Introduction

7. Introduction

8. Introduction

9. Introduction

10. Introduction

11. Introduction

12. Particles…not that good.
First Method: spectra-photometry
First method used: Spectrophotometry, assume transmission losses are due to
Absorption….big detector on other side….sort of OK, but b/(a+b) around 0.8 for
Particles…not that good.
Cuvette with water
Incident beam
Transmitted beam
Large errors due to scattering, but works for dissolved (filtered water)
materials

13. Filter pad (water has been filtered with this)
Filter Pad Absorption techniques
Basis for Filter pad absorption techniques used for concentrated samples
Filter pad (water has been filtered with this)
Incident beam
Transmitted beam
Errors due to backscattering, also a nebulous term “path length amplification”,
But absorption related to transmission and volume of water filtered.

14. Sort of like a transmissometer. Depends on forward
Shiny Tube Absorption meter
Sort of like a transmissometer.
Depends on forward
scattering pattern of
particulates in the water.
Basis for widely used Wetlabs AC-9 and
AC-S
Has to have a scattering correction
(Backscattering, and large angle forward
scattering)

15. Photo-Acoustics

16. Photo-Acoustic Signal

17. Photo thermal

18. Integrating Cavity

19. Introduction

20. Gershuns Law

21. Gershuns Law

22. Introduction

23. Introduction