Underwater Light: Newsletter Challenge (12/02/08)

Here's a better way to look analyze the issue:

Shine a flashlight through a curved hollow pipe. Does any light emerge at the other end? Of course not, thus proving that light has no particle properties. Sometimes physicians need the formulae to be stable more than they need the application to be correct.

The beam of light does NOT remain unchanged. The refractive index of water is higher than that of air. The first challenge is to point the beam of light at the bubble of air. As the light hits the water it is refracted (bent). This is eveident as you view an object underwater. It usually looks to be closer to you (nearer the shore) than it would would be in actuality. Through trial and error you can get the beam of light pointed onto the bubble of air, but as it enters the bubble, it is bent again and then once more when it leaves the bubble back into the water. How it is bent would be determined by the shape of the bubble both as it enters and leaves. As the bubble will tend to be round, it is very probable that the bubble will act like a prism and scatter the light into its spectral components, a rainbow, but would not effect all of the color the same, depending on the angle the light hit the bubble.

Look, people, the fact that you can see the bubble at all means it has some effect on the light's direction, does it not? If the torch is the only source of light and if you can easily see the bubble at right angles to the beam, how then is a portion of that beam diverted to your eyes if the bubble has no effect on the light's direction? According some here -- thank Bog not all -- you'd think the light enters the bubble then exits and proceeds along its original path as if nothing happened! Bog almighty.

What the hell ever happened to Common Sense?

"When the light emerges from the bubble, does it remain unchanged?"

(Note: This is a simple Yes/No/I Don't Know question.)

No, the light does not remain unchanged. You can see the bubble.

As an old SCUBA diver, an air bubble assumes a convex (mushroom) shape as it rises in the water and I'm sure that the light would be changed.

Pronoun Abuse. Good point. One GA coming right up. Not bad for your very first post (as a member).

Welcome to the Asylum, Mr. Redfred.

Hi, redfred!

Fluorescing.

And I echo ALL of europium's sentiments.

Welcome.

Great first posting as a member. GA

Neat concept: pronoun definition in the question. Liked it. The light from how many flashlights would it take to stop a speeding train? Or stop a Greek invasion?

Mark

"The light from how many flashlights would it take to stop a speeding train?"

Just one, if you don't mind waiting awhile...

Hi, eropium!

I realize that if you "wait awhile", while standing in the rail bed manning your billion or so flashlights, you're in danger of being the reason the train stops. And it's an answer. But not one that addresses the question.

Mark

No, I'm using just one flashlight, which I duct-taped to the front of the locomotive (over the objections of the engineer, who was Greek and didn't speak a lick of English). Sorry I didn't answer your question, but I was really busy, you know? Loading Greek invaders onto flatcars (don't those guys ever shower?) takes a lot of time, not to mention having to run one squad over to Sam's Club for more batteries.

Thanks Mark for the spelling correction. (an sc in fluorescing somehow seems redundant)

But after further thought, I'm going to ammend my flashlight and bubble answer. As we all know the great undefined "it" is not a pronoun, but the acronym for Internet Technology. Since the flashlight, nor the bubble have a Mac address, let alone an IP address, the Internet remains the same.

But wait a minute, I am typing now into the great amorphous digital blob (blog?) about this silly wet flashlight. But this is just one of millions of amusing distractions found in the net. So, I'm back to my same conclusion. Internet Technology remains unchanged.

Hmmm, is this off topic or back to topic?

Who cares? This is still fun.

Redfred

No.

It doesn't remain unchanged.

Principle: Refraction of Light (Due to change in medium)

Just depends on the angle of incidince to the inner surface of the bubble. If the beam approaches with an angle lesser then the critical and brewster angles, the rule " passages to denser medium, approaches to the normal line" applies. the frequency inside water will be different then the one in air, so color of the beam will change to.

Regarding the angle it is possible that, when angle is equal to some specific value, the beam is completely reflected (fiber-optical principle) or follows the surface of the bubble. those specific angles are functions of the electromagnetic properties of the water and air. the salt rate of the water will be very effective.

Regarding the salt density (and so magnetic permeability, conductivity or susceptance etc...), the beam may completely be eliminated within a short length or keep travelling some distances.

If you are on an air bubble, it will not be smart to transmit a beam of high frequency. One may prefer lesser frequencies.

For further knowledge see Engineering Electromagnetics of Cheng.

OK now I am no more guest, the above reply was mine

giving again "

Just depends on the angle of incidince to the inner surface of the bubble. If the beam approaches with an angle lesser then the critical and brewster angles, the rule " passages to denser medium, approaches to the normal line" applies. the frequency inside water will be different then the one in air, so color of the beam will change to.

Regarding the angle it is possible that, when angle is equal to some specific value, the beam is completely reflected (fiber-optical principle) or follows the surface of the bubble. those specific angles are functions of the electromagnetic properties of the water and air. the salt rate of the water will be very effective.

Regarding the salt density (and so magnetic permeability, conductivity or susceptance etc...), the beam may completely be eliminated within a short length or keep travelling some distances.

If you are on an air bubble, it will not be smart to transmit a beam of high frequency. One may prefer lesser frequencies.

For further knowledge see Engineering Electromagnetics of Cheng. "

yes

When The Light Emerges from The bubble it will be multi colored as the surface of the bubble acts like a prism.

The Answer will be posted right here on CR4 on January 6th.

Well?

It's still Jan 6th, even in the UK. And an "official" answer has been posted. Such a shame it's wrong.

I posted "Well?" before the answer was posted.

The Newsletter Challenge answer is "Yes."

The description is wrong. Dead wrong. And incomplete.

Q="Does it remain unchanged?"
Correct answer (not actually given) = "No"
. (Note even if we interpret the question as being changes after the light has left the bubble it is diverging, scattered, and subject to varying Brillouin [and lesser Sommerfeld] precursors).

And (as you say) the description could not be more wrong if they tried.
. (Note: Kris showed some basic reflections [including Total Internal] in post #7)

Fyz

Yeah, it's "No, it does not remain unchanged."

I know better than to post anything before the morning's first gallon of coffee, and it shows. This has happened before.

Me shut up now and go sit in the back.

Look, if you wanna post anonymously, then stop signing your Guest posts "Fyz." It's very confusing, you know, and I've told you this before.

Now go to your room.

I must be missing something. You say the official answer has now been posted. Where is it - somewhere on this page?

It's a one-liner buried in all the visual noise near the top of the page. If you don't see it, use your browser's 'find' facility to search for "And the answer is."

I have to use this facility from time to time because my eyesight is so bad and can't be corrected. 'Twould be nice if the page layout were less cluttered.

If you are going to get the official answer wrong, why not do it magnificently?

If we assume a spherical bubble, the central part of it will act as a negative lens (as described by johnfotl in #3, and elaborated by kris in #7); that part of the light will appear to come from a point between the torch and the bubble...

This 'answer' is just plain wrong. Can you 'show your work'? A raytrace would be fine.

Maybe the balls-up answer was derived from using this aplet ;

http://www.mtholyoke.edu/~mpeterso/classes/phys301/geomopti/lenses.html

The questioner just forgot one or ten things.

The answer seems so ridiculously wrong. Imagine if the bubble were indeed a positive lens and concentrate light in a point. Then, it is possible - given the light source is strong enough and the bubble as symmetrical as possible - that at this focal point the temperature rises enough to locally boil the liquid and create yet another bubble, which in its turn focus light to other focal point, and so on...

Of course, there are issues like diffraction grating due to temperature grating, etc. which may prevent the light from converging to one point (any expert opinion on that?), but anyway, with such magical bubbles we would experience some very interesting phenomena.

Here's photographic proof of the answer - a torch is being shone through a bubble in deep water. you'll just have to take my word on it.

Look out for the next challenge, "White Cat at the North Pole".

Does Fyz know you borrowed his avatar?

Hi, Kris!

With regard to your response #132 (above), I concur. With the exception of one or two small details, that photograph is quite similar to not a few obtained during our experiment (response #9).

[While this second (response #136) shot obviously bears small resemblance to the former to the expert observer, it is remarkable that similar results can be obtained anywhere in the world: as witness this second shot of the cat at the 'pole, obtained with neither a flashlight nor a bubble; but merely the clever utilization of ideal chronometric conditions and feline species as near substitutes. A remote conjecture might bring up the possibilities of interchange of cats, bubbles, winter, water, and flashlights to determine whether there is indeed any connection to the OP.]

Mark