web analytics

Wherein Weasel channels Mr Wizard


Illustration pinched from this fun introduction to optical microscopy

Refractive index is a measure of how much light is bent — or, to put it another way, slowed down — by a transparent or translucent material. Light moves through water 1.33 times slower than it does through a vacuum, so the refractive index of water is 1.33.

Oh, half y’all are physics geeks. You know this. I only know it because when I was a kid I thought I could invent an iridescent surface by combining painting materials with greatly different refractive indices. A thin layer of something on top of a thick layer of something with a very different RI will make a rainbow. Soap bubbles. Motor oil in a water puddle.

I failed, but let’s not dwell on that.

All this is by way of introduction to this cool video I ran across this evening. Because they have identical refractive indices, this is what happens when you dip a borosilicate rod (i.e. what Pyrex used to be before they changed the formula) into a beaker of cooking oil or glycerin.

I feel terribly, terribly cheated that real scientists don’t sit around doing this kind of shit all day.


Comment from Uncle Badger
Time: February 1, 2016, 11:17 pm

Huh! You’re fooling no one, Weasel! It went up his sleeve.

Comment from mojo
Time: February 2, 2016, 12:20 am

Same deal with diamonds in water.

Comment from AliceH
Time: February 2, 2016, 12:39 am

Ooh ooh! I know this one.

Crime labs use this property of refraction to compare glass evidence to other glass sources like a suspect’s car, or eyeglasses.

They put the crime scene glass in oil and heat the oil until the glass “disappears”, and then do the same for the comparison glass. If the temperature matches, the refraction index is identical, and (they say) proves the two pieces of glass are from the same source.

I think “proves” must be too strong, though. Unless there are infinite refraction indices, and we can detect to infinite precision.

Comment from QuasiModo
Time: February 2, 2016, 12:42 am

Cool fizzicks! :+)

Comment from Pupster
Time: February 2, 2016, 12:50 am



Comment from David Gillies
Time: February 2, 2016, 1:13 am

It’s also how you get toothpaste (like Aquafresh) which has clear gel stripes that nonetheless have abrasive material in them. The abrasive and the gel have the same refractive index.

We measured the refractive index of light in glass with a HeNe laser rigged as a Michelson interferometer in first year undergrad physics. That was many moons ago.

Comment from dissent555
Time: February 2, 2016, 1:53 am

Aw c’mon. Caint be real science unless there are at least 4 flask with different color bubbling liquids. And a bunsen burner or two. And forget all that pesky safety gear too.

Comment from Steamboat McGoo
Time: February 2, 2016, 3:10 am

Somewhere in a storage box I have a bottle of “Crystal-Wax” (or Mop-n-Glo, or whatever the hell it was called) floor wax I bought back in about 1982. It’s claim to fame was that there was a real diamond inside the (clear) bottle – submerged in the “crystal-clear” floor wax.

It was actually a real bitch to see back then. Since then the liquid wax has discolored with age, and its easy to see the itty-bitty diamond laying in there on the bottom.

Comment from Anonymous
Time: February 2, 2016, 6:41 am

This is how they ID glass from crime scenes, too. Interesting stuff!

(Full disclosure: I am a biology teacher, not physics)

Comment from SCOTTtheBADGER
Time: February 2, 2016, 9:05 am

Mr. Wizaed? As in ” Drizzle Drozzle Druzzle Drome, time for this one to come home “? Tooter the Turtle and all that?

By the way CRUZ WON IOWA! Soon, hopefully, Donald will be going, ” Help me Mr. Wizard, I don’t want to be candidate anymore! “

Comment from Steamboat McGoo
Time: February 2, 2016, 12:43 pm

…. and you made Drudge (again!), Stoaty!


Comment from nightfly
Time: February 2, 2016, 2:56 pm

EXCLUSIVE Romulan cloaking technology REVEALED must credit Stoaty

Comment from Wolfus Aurelius
Time: February 2, 2016, 3:26 pm

I seem to recall Wells had his Invisible Man mention something like it in the novel. The diamond in water thing, maybe.

Comment from Deborah HH
Time: February 2, 2016, 6:47 pm

And wasn’t there an episode of the A-Team that used the diamonds in the water cooler trick? I have a vague memory of BA (Mr.T) hefting that 40 lb/5-gallon jug of water on his shoulder.

Groundhog Day, too. Punxsutawney Phil didn’t see his shadow. I am always surprised by how many people identify “Groundhog Day” as their favorite movie.

Comment from Steamboat McGoo
Time: February 2, 2016, 8:44 pm

And there was a Wild, Wild West episode where the Bad Guy was stealing & burning diamonds (into some magic elixir) to make him super-fast – so fast that he couldn’t even be seen.

God, I loved that show – especially the Dr. Loveless stories.

And…wasn’t there a military movie about hiding smuggled diamonds in water-cooler-jugs of drinking water. It took place on that fancy military base in San Francisco – “The Citidal”, or sumpin?

Comment from dissent555
Time: February 2, 2016, 9:34 pm

Magoo, I think you’re referring to “The Presidio”.

Comment from Steamboat McGoo
Time: February 2, 2016, 11:20 pm

Yep. That’s the one, dissent555. Thx!

Comment from LesterIII
Time: February 3, 2016, 11:45 pm

The Presidio: story featured a powerful-thumb maneuver, smuggled diamonds, and Meg Ryan’s erect nipples. Crafty script writing there…

Write a comment

(as if I cared)

(yeah. I'm going to write)

(oooo! you have a website?)

Beware: more than one link in a comment is apt to earn you a trip to the spam filter, where you will remain -- cold, frightened and alone -- until I remember to clean the trap. But, hey, without Akismet, we'd be up to our asses in...well, ass porn, mostly.

<< carry me back to ol' virginny