How can we know wavelengths color of blue is exactly 480nm?

How can we know wavelengths color of blue is exactly 480nm?

i would like to know the exactly wavelengths of blue color, is it possible to do that? and which way I can find the exact number i want?

thank you so much

Answer 1

[Bjorn Gustavsson]

You can determine the exact wavelength of a colour (emission or reflection) by spectroscopic measurements. That would give you a curve of intensity or brightness as a function of wavelength. That way you can determine the wavelength(s) of "a colour". So that's a physics answer to your first question.

The second question is even more difficult to answer (unless you want a direct "no"). What you perceive as blue might not be the same as what I perceive as blue. What you say is blue will also depend on your light environment - our eyes are remarkable at adjusting to different conditions, one thing that is done automatically is white-balancing to account for different coloured light. What you can do to determine the wavelength-boundaries between blue and other colours is to use a light-source where you can tune the wavelength and intensity and then sweep over the spectrum and determine the limits of colour blue - for you and a larger group of people...

HTH

[kantapon sumontha]

Thank you so much for your answer. If I want to determine the exact wavelength of a blue color in MATLAP program, is it possible? I don't how to find the exact wavelengths in MATLAP.

[Bjorn Gustavsson]

Well, if you have some information of the actual wavelength for the corresponding intensity - then yes in the most trivial sense. If you have an standard digital RGB-type image - then no in every meaningful way. Such images are made with some type of mosaic sensor with 3 or more groups of pixels with coloured filters, giving them different responses to light of different wavelengths. The intensity in the blue-layer is then the integral of all light filtered with the blue pixel filter transmission. This way light of different spectra can end up giving the same RGB-intensities even though the colours of the light hitting the sensor is different in a spectral sense. This works because the cones in our eyes have 3 colour responses. What wavelengths you see in the end will mainly depend on the screen you use for displaying the image...

HTH

[Dennis]

Besides the variation from monitor to monitor there is no exact wavelength for a single color. Even lasers have a linewidth, the blue color of your monitor is rather broad.

However you can of cause take a spectra of a blue image ([0 0 1]), see attachment.