Spectrum of light has red colour at one end. Why should it have violet colour (combination of red and blue) at the other end?


Solution 1

The violet light at the end of the rainbow is emphatically not a combination of red and blue light. The photons are all roughly the same wavelength (roughly 400 nm), which corresponds to violet as seen by the human eye.

The reason we see red and blue light as violet is because our eyes are essentially made up of three types of sensors which respond in certain ways to certain wavelengths. When a combination of red and blue light hits our eye, it produces the same response from those sensors as violet light, but is not by any means the same light.

Solution 2

Violet PIGMENTs are a mix of red and blue. Light mixes differently, in essentially the opposite way. Take a look here: https://sites.google.com/site/scienceofcolour/how-colors-mix


Related videos on Youtube

S C Sawhney
Author by

S C Sawhney

Updated on July 04, 2020


  • S C Sawhney
    S C Sawhney over 3 years

    From one end of the light spectrum colours keep on changing with the red colour at one end. It is anomalous that the colour at the other end should be also a combination of the red colour because violet colour is a combination of red and blue colours.

    • Alfred Centauri
      Alfred Centauri over 6 years
      From my previous life as a TV repairman, I seem to recall that illuminating the red and blue phosphors of a color CRT yielded magenta (for completeness, red + green = yellow and blue + green = cyan). From the linked Wikipedia article: "Magenta is an extra-spectral color, meaning that it is not found in the visible spectrum of light"
  • probably_someone
    probably_someone over 6 years
    And yes, I am aware that red and blue makes magenta, not violet. Just insert whatever color combination makes your eyes see violet, and the rest of the answer is pretty much unchanged.