Why does light diffract into only seven colours?

  • #1
Summary:: If relativity causes wavelengths to change I.e the redshift effect (or blue shift effect for objects moving towards us) does the presence of 7 different colours denote seven different changes?

If the doppler effect shows that direction of trajectory changes wavelength and colour of light does that mean the seven colours of the rainbow are a breakdown of seven different universal direction changes or that an object with a preposterous gravitational mass has entered and left our universe seven time's? Causing the seven different splits in colours of light?
 
  • Skeptical
Likes davenn, russ_watters, weirdoguy and 1 other person

Answers and Replies

  • #2
berkeman
Mentor
60,880
11,265
Summary:: If relativity causes wavelengths to change I.e the redshift effect (or blue shift effect for objects moving towards us) does the presence of 7 different colours denote seven different changes?

If the doppler effect shows that direction of trajectory changes wavelength and colour of light does that mean the seven colours of the rainbow are a breakdown of seven different universal direction changes or that an object with a preposterous gravitational mass has entered and left our universe seven time's? Causing the seven different splits in colours of light?
Welcome to PF. :smile:

The naming of some of the colors is for human convenience; there is actually a continuum of frequencies in the visible spectrum, as with the rest of the EM spectrum:

1631577418393.png

https://en.wikipedia.org/wiki/Light
 
  • Like
Likes sysprog, davenn and russ_watters
  • #3
hutchphd
Science Advisor
Homework Helper
3,766
2,934
But why seven??It is a good Talmudic number and we seem to like it as humans. I really have no idea why we have seven. Do the Inuit describe seven basic colors? When was the spectrum first so divided ?
After all we have only three distinct eye pigments and yet I swear there are seven colors when I look at the rainbow.
Roy G Biv, your rainbow is a mystery to me.
 
  • Like
Likes sysprog and russ_watters
  • #5
hutchphd
Science Advisor
Homework Helper
3,766
2,934
So you have binary vision.
Dangit I see seven colors in the CIE chart too....
 
  • Haha
  • Like
Likes sysprog and berkeman
  • #6
phinds
Science Advisor
Insights Author
Gold Member
17,291
8,692
... does that mean the seven colours of the rainbow are a breakdown of seven different universal direction changes ... ?
No, it means you don't understand the rainbow spectrum. See Berkeman's post directly above.
 
Last edited:
  • #7
vanhees71
Science Advisor
Insights Author
Gold Member
19,092
9,893
One should be aware of the fact that "color" is a physiological rather than a physical phenomenon. It's much more complicated to describe than just the frequencies/wave lenghs in a spectrum of the electromagnetic wave field.

The rainbow is a continuous spectrum, i.e., you have a continuum of frequencies/wave lengths in the solar spectrum (which is pretty much thermal radiation). I also don't see a discrete set of "seven colors" but a continuum in a rainbow.
 
  • Like
Likes sysprog, Pyter, vela and 3 others
  • #8
hutchphd
Science Advisor
Homework Helper
3,766
2,934
  • Like
Likes sysprog, vanhees71 and PeroK
  • #9
PeroK
Science Advisor
Homework Helper
Insights Author
Gold Member
2020 Award
19,296
10,806
I'm not sure we haven't been trolled here. "... an object with a preposterous gravitational mass has entered and left our universe seven times?" Really!
 
  • Like
  • Haha
Likes Delta2 and sysprog
  • #10
berkeman
Mentor
60,880
11,265
I'm not sure we haven't been trolled here. "... an object with a preposterous gravitational mass has entered and left our universe seven times?" Really!
Hah, that's funny. I never finished reading the OP before replying. We'll give him one more day to reply to this thread and go from there...
 
  • Like
Likes sysprog and hutchphd
  • #11
hutchphd
Science Advisor
Homework Helper
3,766
2,934
I'm not sure we haven't been trolled here.
and I got interested in something tangential and wandered off into the woods...
 
  • Haha
  • Like
Likes sysprog and vanhees71
  • #12
PeterDonis
Mentor
Insights Author
2020 Award
35,969
14,013
I see 4096
Obviously you haven't gotten the video card upgrade to 16.7 million colors... :wink:
 
  • Like
  • Haha
  • Wow
Likes Abhishek11235, sysprog, davenn and 4 others
  • #13
phinds
Science Advisor
Insights Author
Gold Member
17,291
8,692
my brain certainly wants to break up that continuum into seven sections
Sure, and if you look carefully you'll see that all 7 of them have shades of color, not just one color.
 
  • Like
Likes sysprog and vanhees71
  • #14
hilbert2
Science Advisor
Insights Author
Gold Member
1,530
553
The human central nervous system (of which the retina is one part) can normally only produce sensations of three primary colors. That limits the amount of nameable colors we can describe. Some people, all of who are women, can sense four primary colors because they have four types of retinal cone cells with different pigments. The ability for this is coded in the X-chromosome, that's why male people can't have that ability. Some species of birds can even sense five primary colors. As far as I know, the US military is preliminarily researching a possibility to make people see infrared radiation with some kind of eye drops that temporarily add new pigment molecules to your retina. That way you could see in the dark and locate people by "seeing" how their body temperature is higher than ambient.

https://en.wikipedia.org/wiki/Tetrachromacy
 
  • Informative
  • Like
Likes sysprog, Pyter, Hamiltonian299792458 and 2 others
  • #15
berkeman
Mentor
60,880
11,265
  • Haha
Likes sysprog and davenn
  • #17
Demystifier
Science Advisor
Insights Author
Gold Member
12,367
4,696
does the presence of 7 different colours denote seven different changes?
No, it represents 7 different sizes of T-shirts: XS, S, M, L, XL, XXL, XXXL. Now if you ask me why in Universe there are no T-shirts of other sizes, it's due to quantization, obviously. Duh! :rolleyes:
 

Attachments

  • A13usaonutL._CLa|2140,2000|714sOzgiM3L.png|0,0,2140,2000+0.0,0.0,2140.0,2000.0_AC_UL1500_.jpeg
    A13usaonutL._CLa|2140,2000|714sOzgiM3L.png|0,0,2140,2000+0.0,0.0,2140.0,2000.0_AC_UL1500_.jpeg
    30.3 KB · Views: 18
Last edited:
  • Haha
  • Like
Likes phinds, sysprog, Pyter and 5 others
  • #18
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
27,661
11,883
There are also seven sizes of olives: medium, large, extra large, jumbo, giant, colossal and super colossal.

Coincidence?

Anyway, I am late for my next universe.
 
  • Haha
  • Like
Likes sysprog, vanhees71, Demystifier and 4 others
  • #19
jim mcnamara
Mentor
4,473
3,245
FWIW - one language I'm familiar with has different names for colors - green turquoise when translated to Navajo is either blue stone or sometimes 'sky' stone because it the same color as the clear sky. In Navajo.
This is not a unique feature of just one language.

Our brains use the language we speak and it's color designations. Plus we get fooled:
Adelson - move your cursor off the line drawn box completely and back onto the checkerboard a couple of times....
https://www.illusionsindex.org/ir/checkershadow
 
  • #20
vela
Staff Emeritus
Science Advisor
Homework Helper
Education Advisor
15,228
1,830
  • Like
  • Informative
Likes russ_watters, DaveC426913, Merlin3189 and 4 others
  • #22
59
31
Fun fact: not all colors are found in the rainbow. There's no magenta, and no cyan. Which proves that "color" isn't just a function of wavelength - it's the end result of our visual and neural systems' processes. (Any yellow you think you see on your computer screen isn't really there ... at least, it's not due to yellow light, which the screen cannot produce.)
Makes you wonder what other colors might be "seen" by different species with different wetware.
 
  • Like
Likes vanhees71 and Pyter
  • #23
Merlin3189
Homework Helper
Gold Member
1,668
777
And I think George Miller might suggest that we generally perceive seven gradations of anything.
 
  • #24
87
39
"Some people, all of who are women, can sense four primary colors..."

So why does my wife only see red when I suggest going for a beer?

When looking at a spectrum, at what point does "red" become "orange" etc.? What we call colours are a man-made concept and because of the way we perceive colour, with three frequency-dependent structures and an amplitude-dependent structure, we see six basic colours plus black and white as well as every shade in between.
 
  • Like
  • Haha
Likes russ_watters and davenn
  • #25
DaveC426913
Gold Member
20,083
3,388
  • Like
Likes nasu, russ_watters and hutchphd

Related Threads on Why does light diffract into only seven colours?

  • Last Post
Replies
8
Views
13K
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
17
Views
2K
  • Last Post
Replies
1
Views
944
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
8
Views
2K
  • Last Post
Replies
9
Views
2K
  • Last Post
Replies
6
Views
3K
  • Last Post
2
Replies
42
Views
7K
Top