Irridescent Scales - How does it happen?

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slim6y

Almost Legendary
Recently (as early as the very early am) a thread was presented about what you don't like about aussie snakes.

Someone who shall remain nameless (sax) suggested antaresia were extremely ugly and boring.

But the one thing that came extremely clear to me, when owning antaresia, was their striking colours when they shimmered in the daytime sun.

A beautiful rainbow of reflection off their scales. The pearlescent paint they put on their scales really works...

I know why they're so closely related to the actual rainbow serpent - but it doesn't change the fact that so many people will just be amazed at the colour that reflects from the snake in the right light conditions.

But how does it happen?

Well lucky for you I'm meant to be marking Physics (level 3) exams right now, so... Instead of working I'm going to see if I can explain thin film interference and relate it to a snake's scales!

If you've ever seen a soap bubble glistening the rainbow off its surface, or even an oil spill (tiny amounts) on a small water puddle, or even a CD/DVD that reflects the colours of the rainbow... All these work in roughly the same way as scales reflecting light.

My explanation could be a little 'basic' in parts, because I haven't a clue what general knowledge anyone has, and I am really only wasting time because I hate marking exams so much!!!

So... Lets start:

Light can mix with 'other' light to cause a multitude of colours. So if I mix yellow light with red light I get....

White light is actually a mixture of ALL light colours. So if I was to split white light up into everything, I'd see a rainbow of colours. In fact, I'd see the rainbow, but... You'd be surprised what else you're missing out on. No infra red, no ultra violet... None of those colours are visible to our feeble eyes.

Actually, if anyone wants to take a photo of a rainbow using an infra-red camera, I'd be quite keen to see the infra-red part of the rainbow.... Even better, could someone use a similar camera to get a photo of the thin film interference off a snake scale? Unfortunately, in NZ, I am out of snakes to do this with!

So - to continue your lesson.

When light shines down on to the scale, some of the light is reflected back off the scale and some of the light passes through the scale.

The light that passes through the scale might reflect off the bottom surface of the scale and back out of the top surface. The size difference of these surfaces is possibly just microns thick (millionths of a metre).

The light that reflects from the bottom of the scale mixes back with the light that reflected off the top of scale. That mixing gives rise to the colours.

But... Sorry, there's still more:



Where it says soap bubble replace that word with snake scale.

Refraction occurs at the top end of the scale (this is bending of light essentially) and reflection also occurs.

Because the gap is so small, the reflection that occurs from the refracted light at the bottom of the scale returns at the same angle and mixes with the reflected light from the top of the scale causing that colour change.

If the scale had varying thicknesses we'd actually be seeing far more colours - because we only see a typical amount of colours (in my opinion on the blue side of the spectrum) I would guess the scale is roughly similar proportion of size all the way through.

Would anyone care to elaborate on the functionality of this colouring? Where would snakes even use this colouring and for what purpose?

Is reflecting blue (hues) important for a snake?

Well, thus concludes my lesson on thin film interference - in brief... There;s no harm in learning why now is there?
 

euphorion

Very Well-Known Member
Hahahaaaa, high school physics. This was one of the few things i actually enjoyed, "oooooooh pretty!"
 

slim6y

Almost Legendary
A quick bit of research suggests that snake scales might be 'ridged' so the effect is more similar to that from a CD than from a soap bubble.

The reasons could be - lowering friction (and adherence of substrates) to lowering the wetability of the scale so that the scales act as a water repellent.

This would mean that the interference is merely a by-product as a result of some other function.
 

Rob

Administrator
Staff member
Interesting post, although I do have to wonder if the people who say ants are boring have seen some of the work that people like Peter Birch have been doing recently.
 

Stuart

Site Admin
Staff member
I actually enjoyed reading that, thanks slim6y.

Now I want to cover my Stimsons in soap to get an even better rainbow effect...
 

lmnw57

Not so new Member
personally love antaresia and a very intersting post enjoyed it ps i dont think they are ugly some have the best nature and if you sit and watch while they are active even feeding they do some pretty funny stuff
 

Rob

Administrator
Staff member
His website appears to have been hacked, so no info there, but he's working on various different morphs - blondes, ghosts, platinums, etc.

Here are various pics from his FB:
















"Boring" certainly isn't a word I'd use.
 
F

FAY

Guest
Funny you should bring this up Slim. I have a couple of Elcho Island childreni. The seem to look like they have sparkles down their back. It is very strange. Not sure if I could get a good picture of it.
 

slim6y

Almost Legendary
It's hard to get good photos of this effect - firstly getting the snake to stay still in the sun and secondly, the camera misses some of the colours.

But take a photo anyway - I'm keen to see the shine :)
 

Red-Ink

Very Well-Known Member
I actually enjoyed reading that, thanks slim6y.

Now I want to cover my Stimsons in soap to get an even better rainbow effect...

You dont need soap to capture the irredescence (it can enhance it)...

Angle of incidence = the angle of reflectance..

Take a pic on the opposite side of the light source hitting your snake and you will capture it on camera.

Not the best example of it as this shot was'nt set up to capture the irredescence but... parts of the snake reflecting the light source from the opposite side of the enclosure to what the camera can see captures it. Direct sunlight is the best light source to capture the "rainbow" effect.

 
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Jande

Well-Known Member
Funny you should bring this up Slim. I have a couple of Elcho Island childreni. The seem to look like they have sparkles down their back. It is very strange. Not sure if I could get a good picture of it.

Was admiring my Elcho girl from Bonustokin (great snake and great guy!) the same way just yesterday. Absolutely stunning rainbow sparkly effect on her. I get so excited when I see she is about to shed as it gets even prettier (if that's even possible). :D

Loving some of those Ants from Peter... well no, I love them ALL! Some very sexy snakes indeed.

And thanks Slim6y for a very interesting read! Maybe I should have taken physics in high school after all. ;)
 

slim6y

Almost Legendary
Jande... I agree on you about Billy... And wpould love to see pics of the Elchos...

Tell me though - does the sheen get better after shed or during shed?

I always found that during shed my girls would look like unspotted pythons. They went so plain and patternless. But because I never disturbed them I never really got to see if the iridescent ability remained.

My initial guess is it doesn't... But when I think about the physics - the thin film remains the same thickness for the outer skin so why couldn't the effect remain?
 

Red-Ink

Very Well-Known Member
My initial guess is it doesn't... But when I think about the physics - the thin film remains the same thickness for the outer skin so why couldn't the effect remain?

Same thickness but possibly not the same density.. do scales get denser with age?
 
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