White Light and the rest of spectrum.

I don't have time to really explain this properly, but all EM waves travel at the same speed, trust me on this, they are split in a prism because the different wavelengths are bent by different amounts when interacting with matter. So white light, which is made up of a large number of photons of different colours, can be split into these different parts using a prism. Incidentally, here's a pic of the suns emission spectrum:



Note how the peak intensity is actually green... right in the area our eye is most sensitive too

In essence i was trying to figure out what frequency white light has. Based on everyone's replies i am left to understand that white light doesnt have a frequency. This is because its a combination of colors and is not a color itself. For long ive always thought white was a color, but i guess i was wrong. I find it kinda amazing that our brains percieve white as all the colors combined.

Thanks everyone for the replies.

Despite what Slashpepper my have alluded to, by mistake or otherwise, the Sun does not give off blackbody radiation. What was given was a good example of what blackbody radiation emits through the spectrum, though that it says it's what the Sun emits is not entirely true.

A blackbody emits a continuous spectrum, while the Sun has several absorption lines (called Fraunhofer lines, named for the discoverer) blocking off sections of the spectrum.



EDIT: A good example of a blackbody emission would be a light bulb.

[edit on 3/20/2005 by cmdrkeenkid]

Originally posted by Slashpepper
I don't have time to really explain this properly, but all EM waves travel at the same speed, trust me on this, they are split in a prism because the different wavelengths are bent by different amounts when interacting with matter. So white light, which is made up of a large number of photons of different colours, can be split into these different parts using a prism. Incidentally, here's a pic of the suns emission spectrum:



Note how the peak intensity is actually green... right in the area our eye is most sensitive too

Well that explains why when I look at the sun I get a green ball after a while.

Originally posted by Mayet
Well that explains why when I look at the sun I get a green ball after a while.

Or that could be your eye frying... NEVER look at the Sun directly without the aide of filters.

The fact that em waves all travel at the speed of light (c) and since velocity= wavelength*frequency can be used to tell if an object is moving away or towards us thanks to the doppler effect. Hence, when we get redshift it corresponds to something moving away as the wavelength will increase while the frequency decreases (as c must remain constant), the opposite is true for blueshift ie it represents something coming toward us.
These facts can be used to prove that binary stars exist and also the temperature of an object using spectral broadening.

Question: If we could see 100% of the known electromagnetic energy spectrum versus the 2% of "visible light" we currently see, would we still perceive the culmination of all the EM frequencies as white light?

If yes then the color white is even more interesting to me. We cannot fathom what the other frequencies (colors) look like but we can at least find comfort in that fact that white light is a constant.

If that made little sense or was completely uneducted then I apologize.

[edit on 073131p://21u07 by Lucid Lunacy]

Originally posted by cmdrkeenkid

Originally posted by Mayet
Well that explains why when I look at the sun I get a green ball after a while.

Or that could be your eye frying... NEVER look at the Sun directly without the aide of filters.

I actually have been doing it for years...my eyes are fine

[edit on 22-3-2005 by Mayet]

red light does not move faster than blue. when white light goes through a prism of any sorts the longer wavelengths of light get refracted more than the shorter ones. since we all know that light through a vaccum travels at 186k a second and much slower through other substances (diamonds slow light down quite a bit)

draw yourself a triangle, next draw a straight line heading towards the triangle, different lengths of lines would represent different wave lengths. when the line hits the triangle only the part of the line, or wave, that hits is slowed and bent and continues to bend untill the entire wave has entered the triangle/prism. now do the same with a shorter line/wave length. as with the longer one it slows and is bent/refracted the same way, but since its entire wave has entered the prism it quits being refracted until it leaves the prisim where the same thing happens again

Originally posted by Lucid Lunacy
Question: If we could see 100% of the known electromagnetic energy spectrum versus the 2% of "visible light" we currently see, would we still perceive the culmination of all the EM frequencies as white light?

If yes then the color white is even more interesting to me. We cannot fathom what the other frequencies (colors) look like but we can at least find comfort in that fact that white light is a constant.

If that made little sense or was completely uneducted then I apologize.

[edit on 073131p://21u07 by Lucid Lunacy]

Very interesting point.

I was wondering this myself. The other wavelengths wouldn't really be a "color" if we could percieve them, would they?....Since they are seperate from "colors" in the EM spectrum

This will always be anecdotal, but its still kinda interesting to think about it, considering no one can ever give us an answer.

my best guess is that it would all be lumped into one. when we see colors of light, like say a tree leaf, what we are seing is only the light that the leaf does not abbsorb. so i would tend to think that if we had a much broader perception from ulta violet to infrared we would see the whole as "white"

Here's a good illustration showing how white light is created from HowStuffWorks. And it's true, white light doesn't have a wavelength. It's just what we percieve when we see all of the visible wavelengths at the same time. So, in essence, white light is an illusion. Trying to average out a "hypothetical" number here is like trying to add average out the most commonly used letter in a paragraph and if that letter were say, "e", calling the whole sentance "e". The problem is that white light literally is more than the sum of its parts. Hope this helps.

LINK

Oh!,....By the way, Look at the Pixels on your computer monitor or television set. When you view a "White" area,.....youll notice that all three colors are lit up! But you only see that when you get close. From far away, it looks like white.

[edit on 22-3-2005 by spike]

I think that if we were to see all the colors there are, the spectrum would stay the same, but just spread out over more wavelengths.