I have understood the general concept of electromagnetic waves since I was at school, and now I have delved into the harder part of physics with an extended desire to study astrophysics. I was taught at school that light is within the visible part of the electromagnetic spectrum, and so we perceive light and it's frequencies as colour through light.

But what I had failed to recognise was that light doesn't really have a spectrum of colours but a spectrum of frequencies that we perceive as colours. So this had become a shock to me because now I have had to realise that colour is psychological and not physical as we would apprehend.

I think schools should point this out very clearly whenever they talk about light as "the visible part of the spectrum". Visible to our mind, 'yes'! But not to an observor in reality.

colour is indeed a certain frequency range (of the EM spectrum) which is 'picked up' by or detected by 'sensors' in our eyes.

 

if you had weird mutated eyes that picked up a lower or higher frequency compared to visible light then they would 'see' infa-red or ultraviolet.

 

Visible to our mind, 'yes'! But not to an observor in reality.

i would say visible to anyone who has sensory organs such as eyes (if eyes count as organs?) that can detect (any or a part of) the EM spectrum.

I read recently that our eyes have what is called a 'colour constancy' which helps us visualise one colour even though the frequencies from that source may change. In other words it prevents us from seeing objects that evolve into a multitude of colours.

Just to correct that statement, I said the "eye", but I was meant to say the 'brain'!

i dont know, i havent heard of that although when it comes to biology i havent heard much!

 

what i know is that eyes sense the incoming EM waves of a certain frequency (visible light) and makes that into an electrical signal which goes to the brain, which then makes an image of what we 'see'.

Color constancy is a real thing, researched by psychologists for many years. Basically our perception of color is not only determined by the actual wavelengths hitting our eyes, it is also influenced by many factors such as the surrounding context of colors, what color we may expect to see from a certain object and also the relationship of the actual color of an object, and the wavelength of light that is being reflected off of it (like shining a blue light on a red wall). Generally people can retain color constancy, but it can break down in certain situations.