White Light's frequency

[NanakiXIII]

If you look at the electromagnetic spectrum, mainly at the light part, white isn't included. Which is logical since white is all colours. But what frequency does white light have then?

[Kedas]

All of them :)

[NanakiXIII]

What would that look like on a oscilloscope (probably spelled that all wrong)?

[Kedas]

white noise ;)

[NanakiXIII]

What's that?

[Kedas]

your answer :)




Sorry for doing that, use google :)

[NanakiXIII]

Found it. Thanks.

[YT2095]

it does raise an interesting question with regards to pure Red, Green and Blue, at mono frequencies generating "white" light though.
I took is as, "white" anything, is a purely a random dispersion of frequency and amplitude.

so it does raise how with 3 known frequencies, a random event can occur? or is it just to do with the limitations of our eyes?
white light splits into 7 basic colors red, orange,yellow,green,blue, indigo,violet. and all frequencies between. some from 3 calculable elements randomness can occur? or maybe Chaos at a push?

[NanakiXIII]

I didn't get one word of what you were just talking about.

[YT2095]

White light (using addative synthesis) is made of the 3 basic colors Red, Green and Blue.
Subtractive synthesis used what you may have learned in school during Art lesson the "Primary Colors" Red ,Yellow and Blue.

since it`s LIGHT and not reflected colors were discussing, we need to use Addative synthesis :)

hope that helps :)

[YT2095]

AHA! maybe this would be a good way to explain :)

when you draw a picture, the color of your paper is already WHITE! a bit like a sculpter, he has a solid block of stone in front of him, he then takes away all the parts that don`t look like a man using his chissel and hammer, eventualy the block of stone looks like a man. with you and your white paper, you have ALL the colors there reflecting off the page, it`s now up to you to remove all the bits of white to make it look like a man, so you draw on it covering the bits you don`t want with something darker (a pencil, a felt pen, charcoal etc...) OR you use colors pencils or crayons, that will only let certain colors be reflected off them.

now, with light, it`s the opposite :) you sit in a dark room with a screen and lots of different colored lights. a bit like the same sculpter sitting there in front of an empty table with a bag of clay, he will then ADD all the bits that look like a man or shape the ones that don`t, you may use your lights to make different colors :)
that`s ADDATIVE synthesis :)

now I REALLY HOPE that helps a little, the idea`s sound even if the spelling sux :)

[NanakiXIII]

That makes sense. Thanks.

[Sayonara³]

Wavelength :lclambda: affects colour, not frequency.

[VendingMenace]

Wavelength affects colour, not frequency.


If you specify the frequency of light you are also specifying the wavelength.

(frequency) * (wavelength) = (speed of light)

since speed of light is constant. Specifying frequency or wavelength specifies the other as well. Thus, frequency affect (or rather, determines) color. :)

[alt_f13]

Would it not be frequency that affects color? You get doppler affect with stars etc. that change the frequency at which you recieve the waves, while the wavelenght remains the same.

I see how one can denote the other, but not how wavelength can alone be the determination of color when red/blue shift say otherwise.

Or does the wavelenght change relative to the observer???

edit -- No wait, that doesn't make sense or we wouldn't get the doppler affect on light.

[Kedas]

VendingMenace said in post #14 (http://www.scienceforums.net/forums/showthread.php?s=&postid=22908#post22908):


If you specify the frequency of light you are also specifying the wavelength.

(frequency) * (wavelength) = (speed of light)

since speed of light is constant. Specifying frequency or wavelength specifies the other as well. Thus, frequency affect (or rather, determines) color. :)

not 100% sure but
If a red beam travels through glass it speed will drop and its frequency but the wavelengthy/colour will stay constant

About doppler effect the speed stays the same but the frequency changes and therefore also the colour/wavelength.


EDIT: interresting
Sound seems to be different (or that about light was wrong)
If you breath helium then you get that very funny high voice effect
The 'vocal chamber' to resonate stays the same size so the wavelength is also the same size but the speed of sound in helium is about 3 times faster so the frequency is also 3 times higher.

[YT2095]

frequency and wavelength are inseperable.

our visible spectrum is roughly between 10 -6m and 10 -7m or put another way 10^14hz to 10^15hz.
eye peak response 5.5 x 10 -7m.
frequency and speed are different. wave length is just a funtion of peak to peak distance over time or trough to trough, like on an osciloscope. frequncy is how often it occurs over time.

"If a red beam travels through glass it speed will drop and its frequency but the wavelengthy/colour will stay constant "

if it`s frequency drops it wavelength will increase also.

[Kedas]

YT2095 said in post #17 (http://www.scienceforums.net/forums/showthread.php?s=&postid=22915#post22915):
frequency and wavelength are inseperable.

"If a red beam travels through glass it speed will drop and its frequency but the wavelengthy/colour will stay constant "

if it`s frequency drops it wavelength will increase also.

I did some checking and it's not like I said earlier it's the same like sound the wavelength and speed will change and the frequency will stay constant.
(no, they won't change both if medium changes)

If you think about it it's logical:
every puls that goes in the glass/water has to pass at the same rate otherwise it would mean that the glass/water/etc stores or create information.
So the frequency doesn't change only wavelength and speed.

about if colour is defined by frequency or wavelenth:
So it's the frequency that defines the colour not the wavelength.
It's a bit a pointless discusstion because we always see colour the same way THROUGH our eyes so if colour is defined by frequency or wavelenth no one cares because none can see colour inside an other medium, the medium is always our eyes.
If we talk about a colour/wavelength of 600nm then we always talk about vacuum unless specified.

[YT2095]

well the question I had, was how does white light get generated by only 3 different colors, Red, Green and Blue?.
I took "White" anything as being a purely random mix, whether it be sound or light etc...
but using only 3 definable components (mathematicly) how can that create what is seemingly "Chaos"?

also to address your other point about light in a glass medium, it stores, it doesn`t create. on saturation it radiates lateraly, this principal is exploited in many Laser designs :)

[JaKiri]

Because the qualitative experience of colour is generated by the proccessing of data from the eyes in the nervous system - the different colour bands are NOT a property of light itself. It is not certain why the optic system does it this way instead of just specifying the properties of the incoming light quantitatively, but it seems likely that a system which triggers discrete responses at certain thresholds is easier to produce.

the ability of nerves to specify quantitative information is limited. they can only be "on" or "off", so things like the intensity of pain are communicated by the frequency of pulses. However, a nerve can only pulse at a finite rate, setting an upper limit. The lower limit is set by the interval at which seperate pulses indicate seperate "inputs" - making this longer costs "resolution" of sensations in time, so there is a limit on this too.

EDIT - this is giles, but i cba logging out of mark's account, since i'm on his PC anyway.

[YT2095]

the ability of nerves to specify quantitative information is limited. they can only be "on" or "off", so things like the intensity of pain are communicated by the frequency of pulses. However, a nerve can only pulse at a finite rate, setting an upper limit. The lower limit is set by the interval at which seperate pulses indicate seperate "inputs" - making this longer costs "resolution" of sensations in time, so there is a limit on this too.

sorry... ignore this post, I still aint got the hang of this "Quote" thingy yet :(

[YT2095]

but that`s almost like saying and extremely mild pain would be a series of MAX pains at interval? like morse code.
I agree that when an acetylcholine molecule jumps a gap and "makes a circuit" sure it`s on / off, but a single molecule would be hardly be even noticable (if at all) so for us, it is more of an analogue process, hence we notice declining light or mild to extreme pain and all the bits in between, but certainly not as black and white as you stated surely?

Don`t misunderstand me, I do agree with what your saying to a point, examining the retina and "image rettention" for example displays the properties you mention, a TV picture flickers at a certain rate and we see it as a continued image as if in real life, and below this freq we see the flicker, but for pain? I do thing think there are alot more "shades of grey" than on/off

[fafalone]

Kedas said in post #18 (http://www.scienceforums.net/forums/showthread.php?s=&postid=22957#post22957):




If you think about it it's logical:
every puls that goes in the glass/water has to pass at the same rate otherwise it would mean that the glass/water/etc stores or create information.


Actually I believe they have developed a material that stores light and emits it later. Very interesting.

[YT2095]

Zinc Sulphide will do such a job also, it`s the stuff they use on NEWER clock faces or the glow-in-the-dark stickers you sometimes get for free in breakfast cerial :)

[swansont]

YT2095 said in post #17 (http://www.scienceforums.net/forums/showthread.php?s=&postid=22915#post22915):
frequency and wavelength are inseperable.
"If a red beam travels through glass it speed will drop and its frequency but the wavelengthy/colour will stay constant "

if it`s frequency drops it wavelength will increase also.

In a medium (n>1) the wavelength becomes lambda/n. The frequency stays the same. Light travels at c/n through the medium.

[Sayonara³]

Am I right yet?

[Kedas]

Sayonara³ said in post #26 (http://www.scienceforums.net/forums/showthread.php?s=&postid=23298#post23298):
Am I right yet?

No, not yet. You must be patient.
Do you know how long it took before we believed that the earth wasn't flat ? ;)

[YT2095]

Hopefully sometime 2moro I shall be conducting an experiment with this "white light" idea.
I`ve mannaged to get hold of a really rather fascinating semiconductor, in effect, it`s 3 mono frequency LED`s (Light Emiting Diodes" on the same silicon substrate, each of the 3 colors Red, Green and Blue can be controlled individualy, although the Red control seems to like it`s current alot more than the green and blue (easily compensated for).
I`m now working on a digital color selector, so I`ll be able to go through all 7 colors of the rainbow :)
incl White light :)
from the white light, I`ll color split it back to it`s new color components with a prism... I`ll let you all know the results :)

[Kedas]

So if I understand your test right, you will generate for example yellow (with red and green) sent that yellow light through a prisma and look which colour(s) you will see after the prisma?
- only yellow
- red and green
- red, green and yellow.

RGB and wavelength on this site:
http://www.physics.sfasu.edu/astro/color/spectra.html

[YT2095]

yup, that about sums it up perfectly as to my plan, I do also plan on using the raw light 1`st and then passing it through a frosted glass filter next.
I wish to determine whether or not an external "scrambler" type influence plays a part also. so 2 tests really.

1) direct pure light through a prism
2) same light through a frosted diffuser then through a prism

[Dudde]

YT2095 said in post #21 (http://www.scienceforums.net/forums/showthread.php?s=&postid=22960#post22960):
sorry... ignore this post, I still aint got the hang of this "Quote" thingy yet :(

click the checkbox at the top right of the post and click "post reply", or click "quote" at the bottom right, or type [ quote] [/ quote ] around whatever you're quoting

interesting conversation

[YT2095]

Thnx Dudde :)

well the experiment maybe a little deyaled for today, I`ve run out of glue sticks for my glue gun, and being sunday, there`s not much open. I SHALL tae some pics and post them though, if the cam will work at low light levels, as I`ll try and do this in total darkness to avoid external light contamination.
I`de use blu-tak for the lens`s no problem, but the electronics needs proper securing. not to worry though, I`ll find a way :)

[Dudde]

I have a glue stick for a glue gun!
..I don't have a glue gun

nor do I have a use for a glue gun

but I've got the stick