Tele �500 Crossword 20/12

[gardenknowin]

Excellent GK Xword, methinks - bot -ooer - 78A Since when has green been a primary colour?! Surely it should be yellow?

[Catron]

http://en.wikipedia.org/wiki/Primary_color

[gardenknowin]

Thanks Catron - I hereby grovel profusely ! Not what I remember from Science at school (though that was long, long ago....) Have a good Christmas. gk

[hadrianjeffs]

Wikipedia is, as frequently so, wrong.

Primary colours are BLUE, RED & YELLOw. GREEN can not be a primary colour because it is divisible into BLUE & YELLOW, neither of which are divisible except into variations of the primary colour.

The error is due to a practical application. The phosphor dots on old-fashioned TV's are BLUE, RED & GREEN, but this is due to convenience.

[Catron]

This has come up before in answerbank - see here:

http://www.theanswerbank.co.uk/Science/Questio n484039.html

[BigDave44]

It's fairly obvious from the above that the determination of which are the primary colours depends on whether you are speaking of transmitted or reflected light. As usual, Chambers covers all the situations. This is from the online dictionary:

primary colour noun
1 said of lights: any of the three colours (red, green and blue-violet) which together give white light, but can also be combined in various proportions to give all the other colours of the spectrum.
2 said of mixing pigments: any of the three colours (red, yellow and blue) which together give black, but can also be combined in various proportions to give all the other colours of the spectrum.

[Catron]

Nothing to say, hadrianjeffs?