Just so -- that's the point of the illustration of additive (light) primaries, and subtractive (absorbing dyes) primaries.

@@mbanks11 kzbin.info/www/bejne/oaS2XnmAaKdrhcksi=irP29B33a36HnCX3

@@mbanks11 COULD ALSO PERCEIVE IT AS CHARTER FOR SKY COLOR

Sure - you need a way to see the infrared beam, of course. The easiest is a ccd camera or webcam with a lens *not* coated to block IR (consumer models often do). A video camera with ‘night vision’ works, and can display on a computer monitor as does a ccd camera. Lastly, an IR card will let you find the beam, but you usually do *not* want to make a hole through this card.

In principle a doublet has been centred correctly and then cemented at the time of assembly, and therefore you just need to align in reference to the outside surfaces. Finding second-surfaces, the interface between the cemented optics, is a bit harder to see because the different types of glass will be nearly index-matched, and make only a slight Fresnel (interface, internal surfaces) reflection.

You make a square hole. :|

I'm glad you like it!

Yes indeed, as for all oscillations. It's more interesting than you might guess: short pulses of sound, or of light, need more frequency range to compose the rapid changes. Lasers now make pulses of light that are as sort as a few femtoseconds, and to do that they are not at all one pure colour, but many many colours. In fact, the frequencies or wavelengths of light then span *more* than one octave, from below green around 500nm wavelength all the way into the near-infrared at 1100nm and beyond. There's more here about the principles of this: kzbin.info/www/bejne/bWWceImAfbBmfbM

You have hurt me in ways I cannot describe

Oh god, anything but amogus

Gosh no, here's the actual scoop: en.wikipedia.org/wiki/Cone_cell#/media/File:Cone-fundamentals-with-srgb-spectrum.svg

@@mbanks11 The first responds the most to light of longer wavelengths, peaking at about 560 nm; this type is sometimes designated L for long, the majority of the human cones are of the long type. The second most common type responds the most to light of medium-wavelength, peaking at 530 nm, and is abbreviated M for medium, making up about a third of cones in the human eye. The third type responds the most to short-wavelength light, peaking at 420 nm, and is designated S now go and see what colors these are

@@lil_weasel219 Your edit fixed it! ;-) Red, M still peaks right in green, and blue. But it’s red that is not so pure - it’s the differential with green that gives the distinct colours... for most of us. People have different numbers of copies of the genes that code for each cone, and so different sensitivities; we really do see different things. And of course colour deficiencies and colour-blindness, by degree. Interestingly, red and green genes are quite similar, compared to blue, leading to the conjecture their difference is a relatively recent development, in evolutionary terms. It fascinated me that while my uncle was red-green colour blind, he could see quite a lot farther into deep blue than his lab partners, while doing undergrad spectroscopy.

@@mbanks11 I know the finesses, I study biology, juat aaagh fack ...fack. Fackin lapsus. 😆🤭🤭🤐 lol Do you know that women who are heterozygous for X linked colourblindness are tetrachromats? :P not necessarily functionalas most of the time the forth cone is too close to the M cone, but sometimes fully functional and that "dichromat" and a"nomalous trichromat" colourblind folk not only miss many colours, but also see some colours regular trichromats dont, because one of their cones has shifted sensitivity? kek

@@mbanks11 I kinda explained to you this Uncle thing :p now you know why edit; aaand the last reply is full of typos lol

RGB LED's activate all their RGB colors at full intensities to make White, although its not perfect.

What do you get, that's *completely* different from white? What does it look like? In the end, it's probably about the filters not each transmitting the same intensity of light -- some may be too transparent, others too dark.

Well, just to clarify, computer screens typically use just R, G, B -- the "additive" primary colours: each phosphor dot or microscopic LED emits light, and the different colours together go to your eye, so there's more light if R + G light up than if just R lights up. So they add. C, M, Y are a separate system of "subtractive" primary colours, they are kind of "anti" R, G, and B -- they're what you have in paint pigments for example, so a blended mix of different colour paints absorbs whatever each of the pigments solo could absorb. Thus there's *less* light reflected. So RGB light added makes white, and CMY pigments added absorb most everything and appear black(ish). Your question is good -- how does this get "read" in the eye to make all the colours we can perceive? Well, R, G, B aren't accidentally chosen, they're chosen to match the receptor types we have in our eyes, which include genetically coded proteins that absorb different colours of light and use the energy to make signals to travel on optic nerves to the brain, where they're understood or interpreted. S cones see blue, M cones mostly green, and L cones more red. So really the R, G, B of the computer screen is 'talking' to the L, M and S cones -- we 'turn on' different cones as long as the light we hit them with falls in their range of sensitivity. So, real colours in a rainbow are single wavelengths of light, and fall neatly in a region where say *two* cones overlap a bit and are both excited -- say, L and M cones. That will make your brain say "hey, it's falling between red and green, that colour is yellow". Then it's enough if we just send TWO colours to your eye, literally R and G, both L and M cones see something again, and your brain thinks exactly what it thought when yellow (in the middle) hit both types of cone. Long answer. But yes, it's basically a trick on your eyes, that we can use just 3 basic colours of light to pretend to be a whole rainbow, plus all the combinations of the rainbow. If you're interested in more, here's information about cones in the eye: en.wikipedia.org/wiki/Cone_cell

@@mbanks11 When 625-750nm red light and 500-565nm green light are combined, the human eye sees the combination as a yellow colored light. However, yellow light also has its own wavelength range of 565-590nm. When the human eye sees 580nm wavelength light, it sees yellow light.

@@Narsuitus Correct. We call them ‘red’ and ‘green’ receptors by their peak sensitivities, but they each span a range of wavelengths. Yellow light stimulates both receptors at once, just as we can do by using simultaneous red and green light. All we know, by perception, is the net response. The system is what we call in math ‘projective’: actual information of what wavelengths were used is lost, and we’re left with a single equivalence.

Yes indeed, you can learn these terms in this video. If you watch it. ;-)

This is a practical application of an Irrational, Imaginary Number: the square root of negative 1, known as i. It seems so counterintuitive as to how or why you conceptually ADD an i value to an equation as a valid coefficient. It SUBTRACTS an imaginary chunk from a 3D object, creating a dent or a beveled edge. For example, if you took out a 1 x 1 cube from a 3 x 3 square, you have to recalculate the surface area on the 3D plane, as well as the new reflective areas by factoring in that MISSING CHUNK as a positive, workable concept to build new calculations upon. If you pointed the sun at a square mirror, the reflective solar light emission angles are calculated at steady on fixed formula. By using imaginary number i as a constant for that missing 1 x 1 square, you can "add" the new missing chunk as a constant for the new reflective light/color emission. IMAGINE THAT.

From the 'likes', looks like you're not alone! Is there any particular part where you get lost or that seems confusing?

Romin Hawk Well, actually you could... there’s a painting technique called “pointillism”, where with a fine brush you lay down separate dots, ‘pixels’ of paint colour, like a TV screen. Then, the *light* reflected from red paint mixes with the light reflected from green paint, and those two colors of light mix, additively. You may recognize Seurat’s famous painting, “A Sunday Afternoon on the Island of La Grande Jatte” where he did this. But if you mix the two pigments together, any light reflecting gives up what red paint absorbs AND it gives up what green paint absorbs - just like the dyes, but a different colour palette. That’s what “subtractive” colour formation does. For more about using pigments to paint pixels, for additive and not subtractive, this one is a good link: en.m.wikipedia.org/wiki/A_Sunday_Afternoon_on_the_Island_of_La_Grande_Jatte

Peter cross Sure - hey, do you know why a bowl of sugar is white, even though a great big pure sugar crystal is clear? Clouds are water, which is clear... It turns out that both water and a sugar crystal reflect around 4% of light hitting a surface, just as you see your reflection in a store window. But that’s once (or twice, when you count it happening again as it passes the far side, the second surface). Now crush up the sugar crystal, or spray the water very finely, and you get 4% for every single surface in the power or mist. Pretty soon all those 4-percents add up, and it’s white, because all the colours going in bounce around in all directions, and come out again diffusely. It’s more obvious if you want to try a little exercise... got a laser pointer? Shine it into your sugar bowl and you can see pretty easily where that skinny pencil of light ends up. All over a little ball. By the way, your sugar only reflects what goes in, so, now it’s red, not white. Got a GREEN laser pointer too...?

Peter cross - Imagine you have a kid who will eat anything, except Brussels sprouts. You lay out a fine buffet, and when you pass later, only Brussels sprouts are on the table. You recognize your kid by what’s left behind, but for sure your kid is not made of Brussels sprouts... :-D It’s a goofy answer, I know, but it’s a lot like how grass “is green” we say, when that’s precisely what is NOT taken in. As for colours that *are* taken in, there are generally speaking different quantum levels, and certain colours of light can “buy” the atom or molecule a jump between specific levels, like getting a promotion. If there’s a match, the light is taken in, that colour is absorbed; if there’s no match, the light passes by and goes unclaimed. BTW, blue skies? Different story: some molecules don’t absorb but do divert or deflect some colors of light. When skies are blue, say in mid-afternoon, it’s Rayleigh scattering: light passing by overhead is scattered down to us, and most of all scattered is blue. Meanwhile, that continuing light, now much depleted of blue? It’s on its way to being someone else’s red sunset, as they look to the west (i.e., these people are far to our east). Beautiful, how that works out...

I imagine a narcissistic bully who boasts about how awesome they are to boost their image. Awesomeness is precisely the trait that they lack the most, their deepest insecurity is *not* being an awesome person. Thus the false mask the narcissist wears is to reflect the quality of awesomeness though they have the other parts of their humanity intact, the way that grass reflects green to the eye because green is the mask that shows through apophasis what the grass is factually not: the full color spectrum. Just like the bully is missing "green-ness" of being awesome ,though he's got all the other colors.

But where does the orange come from?

red and white make pink and blue and red make purple.

@@liliacfury People make tables of colours, recipes really, so that web designers and others can go back to the same standardized colours each time. Orange light is about 3 parts red light and 2 parts green light, and no blue light at all.

mbanks11 thx

Ian Malcolm thx

Mark Younger YEH

Not sure what you mean here by "why"... In a sense, using three primary colours is a trick, it works because you have in your eyes three receptors of light, which correspond roughly to R, G and B. In the end, I don't need to create the right wavelength, because you can't actually process wavelengths. All I need to do is to cause the same stimulation of the R, G, and B cone receptors in your eyes, and I can cause you to send exactly the same signal to your brain as if I had sent one single wavelength of a given colour of the rainbow.

Orange isn't a secondary colour. It is a tertiary.

+LOLFlyingPotatoes It is a primary color in that it occupies a piece of the spectrum between red and yellow with a wavelength of 590-620 nm and a frequency of 505-480 THz. It is not a mixture of other colors.

@@JohnLloydScharf That's true for lots of colours. Primary colours are a thing because of how our vision system is made -- we have genetically coded pigments, in different kinds of cone cells, which respond when they absorb little ranges of colour. These ranges overlap. So actual orange light around 590 nm triggers both the M and L cones (unequally), cones which give us the ability to see green and red, respectively. That mix of signals is what we see, when we see 'pure' orange. However, it's not the only way to give an 'orange signal' to the brain. I can send TWO wavelengths together, green and red in the right amounts, and dial-up the same responses from M and L cones. Voila, the brain again sees orange, even though no light was there at 590 nm. So, 'primary colour' just refers to our cones, our system of interpreting light signals -- that's the system we have to work with, and have to address with a computer monitor. But, yes, it's a kind of a trick -- the right mix of intensities of R & G, separately, gives the same signal on the optical nerves to the brain as does actual monochrome orange light.

Ok good question. He demonstrates it in the video but simply: Light is mixed differently to pigment (paint for example) When all colour on the light spectrum is added together we get white. Pigment is the opposite; when you add all the paint colours together you don't end up with white (absence of colour), we get black! So with paint, which is a pigment, the primary colours are red, blue and green (or magenta, cyan and yellow for printers). These pigments can produce basically all of the colours we can see. Light's primary colours are green, blue and red, which when combined make white and can make any colour in the visible light spectrum by changing the amount of some or all of the given red green and blue component. Hope this helps!

Bingo! The first are "additive primaries" because turning on a new light adds to the intensity; the second are called "subtractive primaries" because mixing in a new pigment absorbs in addition to the original pigment, so the absorptions add and less light results. For mixing paint, actually, the primaries are subtractive just like ink-jet printers -- unless of course you're a pointillist painter, like Georges Seurat. That's painting in dots, pixels effectively, rather than stirring paints together on a palette, and so the reflected light from each separate pint actually is added together. en.wikipedia.org/wiki/Pointillism

Such an interesting topic -- I never agreed with my neighbour about a toy she had, that I called blue and she called green... It turns out that these pigments in the three kinds of cones in our eye that turn light into nerve signals, these pigments are made via specific genes we have. For some people, one gene-component is missing, they do not make the corresponding pigment or cone, and they cannot distinguish that colour from others. For others, it can be a different missing cone, or a change in the pigment to have a different sensitivity. en.wikipedia.org/wiki/Color_blindness#Red.E2.80.93green_color_blindness But we usually have more than one copy of genes like this, and the upshot is that some folks may have fewer copies and end up with a colour deficiency. So for a shared experience, they may consider the colour of the object you both see to be different from what you see. It's pretty hard to really define colours in a way that work equally well for everyone, but blue sky is a pretty good start, because of the way that Rayleigh scattering works, to shower down onto us the blue parts of sunlight passing through the atmosphere above us. Did you ever think about this? With the blue scattered out of sunlight to become your blue sky, the continuing light -- blue-deficient -- goes on to be someone else's red-orange sunset...

It's not a lie those are the visible wave lengths of light. We only have red green and blue cone cells but when we see a lemon all the colors of the rainbow are being obsorded except yellow. When the yellow light is reflected and hits are eyes an are red and green cone fire. When we see something reflect turquoise/cyan light are blue and green cone fire.

Is Indigo really visible in the rainbow or is that something that Isaac Newton made up such that the 7 colors would match the musical scale? It seems that the rainbow colors should have been Red-Orange-Yellow-Green-Cyan-Blue-Violet. And because Violet (or Purple) do not meet with Red, we don't see Magenta as one of the spectral hues of the rainbow. Could it be that Magenta (Pink to some people) is the color of the electromagnetic spectrum like x-rays, gamma rays, infrared, ultraviolet, and microwaves that are invisible to the human eye?

I really don't know mabe he saw the true blue and thought that was indigo and before that he saw cyan and assumed it was blue because so many people think cyan is blue

The same way so many people think magenta is pink

Ah, the rainbow is one *frequency* or wavelength at a time, across the band. But that's not quite the same as saying that's all the colours that exist, because I might want to pass some red and some blue together from the rainbow, but block out green. That's like saying "white light, subtract green" which gives magenta. See for instance at 2:08, and look at the littlest square where all the colours overlap -- when RGB all overlap, that square is white, but as soon as the green is blocked, that white square is instead magenta. It goes back to white when the green patch is returned. In fact, this is the connection between additive primaries and subtractive primaries -- magenta ink 'takes away' the green (it's kind of "anti-green"!) from white light. If you then use cyan to "take away red", you can add magenta and cyan pigments, to take away BOTH green AND red from white room-lights, and you'll get blue ink on the paper! Here's a "subtractive primary" version of the overlaps possible -- not hard to test on your home printer... en.wikipedia.org/wiki/CMYK_color_model#/media/File:SubtractiveColor.svg

Even lasers are not really pure frequencies, but some are amazingly close! Pulsed lasers can span over an octave of frequencies. Perceptually, we don't actually identify all the colours directly, with sensors for each wavelength like a spectrograph has. We have different sensors in basically three bands -- some differences between people, and some of us have more or less copies of the genes for proteins of each colour sensor, and more or less sensitivity (e.g., colour-deficiency, and colour-blindness, but also higher-than-average too). So one wavelength can make a response among three sensor types R, G, B to produce a 'recipe', a formula of scores for each, and this we then interpret. A single colour can then be simulated, to our eyes, by three different colours in the amounts of this recipe, making the same signals in nerves from our eyes, and we won't be able to tell the difference for how it was done.

Sure -- no pigment is truly black, something always is reflected. I was surprised the first time I took India ink (really black!) and just put a few drops into a glass of water! For good-enough pigments it's darker and darker the more you coat onto the paper. But if you don't want to dump all your ink on the page at once just to get it dark enough, it's very practical simply to add in another cartridge in your printer with some really absorbing pigment. It, too, isn't purely black, but the objective isn't to be perfect, it's to be good enough to satisfy the customer! By the way, some of the research I do uses nanoparticles to make materials that are blacker than any ink. We grow wires from nickel metal, but the wires are 70 nanometers across and a few micrometers long. Pure metal nickel normally is extremely shiny and reflective, but these targets are the blackest thing I have ever seen, and reflect less than 2% of the light that goes onto them. Alas, they would clog up an ink-jet printer I think...

Thank you for schooling me.