Light wavelength transmission through ice

  • #1

Main Question or Discussion Point

I am studying hailstones. I have set up an experiment to pass colored light through hail, one color at a time for the colors of the visible spectrum, Red, Orange, Yellow, Green, Blue, Indigo and Violet (ROYGBIV). I have measured the dominate wavelength for each color with a photo spectrometer. I measure the transmission of light with a Extech SDL400 light meter with no hailstone in place and then again with the hailstone in place inside my reflective cone. A seal prevents light from "leaking" around the hailstone such that only light passing through the stone is measured.

This is part of my Ph.D. dissertation. My hypothesis is that shorter wavelength light will have a higher percent passing through the stone that longer wavelengths for cloudy or opaque stones; where as clear stone will have a higher percentage for the longer wavelengths. I describe the stones dominate wavelength as the highest percent passing through the stone that is the longest wavelength. That is to say the the longest wavelength with the highest percent passing describes the opacity of the hailstone.

What I have not been able to explain is why shorter wavelengths do not always have a higher percent passing even on clear stones! It seems to me that clear stones whos dominate wavelength (using the selection method described above) would also have shorter wavelengths with high or at least equal % passing as longer wavelengths. This has not been the case, many times clear stones will have a high percentage of Red or Orange or Yellow with say Red being the highest, but it seems to me that the other shorter wavelengths (Green, Blue, Indigo or Violet) should be the same or equal values.

So how is it that a clear hailstone can have such a high percentage of a long wavelength say R, or O, or Y and have a lower percentage for GBIV?. It does seem fitting that a cloudy or opaque stone would have a higher percent passing for a shorter wavelength color such as Blue, Indigo, or Violet than a longer wavelength such as Red, Orange or Yellow. Each color is measured on at a time such that the observations are discreet.

Most literature suggest that light (of any wavelength) is refracted off of the air bubble shells inside the ice matrix. This makes it logical that with cloudy or opaque (due to trapped micro air bubbles) the shorter wavelengths would have the highest percent; however, this hypothesis is open to type B uncertainty because I can not explain why short wavelength light is a lower percentage that long wavelength light in clear hailstones. Any help, suggestions or constructive criticism would be most appreciated. Please provide authors name, year and publication of references. Thank you very much!
 
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Answers and Replies

  • #3
LURCH
Science Advisor
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Maybe I’ve been misunderstanding this all along, but isn’t it true that as a general rule, longer wavelengths tend to penetrate deeper, while higher frequencies have more of a tendency to scatter? What makes the results counterintuitive?
 

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