• Question: Why are all colours a product of white

    Asked by jessiemooney to Angela, Gabriele, Karen, Maria, Shane on 12 Nov 2013.
    • Photo: Karen McCarthy

      Karen McCarthy answered on 12 Nov 2013:

      Well firstly Jessie, light is made up of different waves, and colour is how we interpret these wavelengths through our eyes. Visible light is only a small part of the electromagnetic spectrum which we can see and distinguish.

      White light contains all the possible colours in the word, which may be on different wavelengths or spectra as they are called, but we can only visualise a few – which we know as the colours of the rainbow. White light contains all these wavelengths together, hence all colours appear to come from white.

    • Photo: Shane Mc Guinness

      Shane Mc Guinness answered on 12 Nov 2013:

      Great question.
      As Karen says, it’s all down to the different forms of light and their wavelengths. Like the strings on a guitar and the different sounds they make, different wavelengths of light (some of which we can see as “colour”) do different things. Imagine white light (coming from the sun for example) as a book. All the pages are stacked together. But when you bend the book all the pages separate out, so you can see the number on the page. That’s exactly what prisms do, or the droplets in clouds, which gives you a rainbow!
      But the even cooler thing is that this light contains so many other things. some of these wavelengths cook your food (in a microwave!) while others allow you to see your bones (x-rays!). So white light isn’t just colour!

      Also, did you know that we still haven’t found out whether light is a wave or a particle!? It has properties of both, like moving in waves, but we can detect the particle that causes these known as photons. The most fundamental thing we know and we can’t even understand that! There are so many questions like this in science. Go answer one!

    • Photo: Gabriele De Chiara

      Gabriele De Chiara answered on 12 Nov 2013:

      Hello, light coming from the sun is composed of rays at different frequencies, in the same way as a melody from a song is composed of sound of different frequencies. Light at different frequencies has a different colour, but only those frequencies in the visible spectrum can be seen by the naked eye. The visible colours are the ones found in the rainbow or in the light emerging from a prism. Ok, so far I have explained that light is made out of many colours, but your question is why summing all the colours we get white. An object that is red is because it absorbs all colours except red which is reflected. For a green object the same and for the blue the same. If your object is made of many dots green, blue and red (the primary colours), very close to each other, then your eye will see the sum of the colours which is white. Try this experiment: take a disk of paper, and draw 10 or more equal slices. Colour each slice of one of the three colours in equal parts. Now make the disk rotate very fast by attaching the center to a pen. You should be able to see white as in here:

      By the way in response to Shane, it is not true that we don’t know what light is made of. It’s made of photons and we have known this for almost a century. Photons move according to quantum theory which is very well understood!

    • Photo: Angela Stevenson

      Angela Stevenson answered on 13 Nov 2013:

      Hi Jessie! That’s a great question! As brilliantly explained by everyone here, white is the emission of all the colours we see. While black is completely opposite from white! It’s the darkest color due to the total absence of light absorption. I just had to add that little bit to this group answer since it’s a great fact 🙂