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[Physltest] [Phys-L] Re: Color (was LED mini-flashlight price break)



To answer the question, not necessarily. I've found that doing color=
mixing with randomly selected filters is very hit-or-miss. I didn't=
understand why, until I got the little set of gels (with transmissio=
n spectra). The colors that you get when layering colored filters, o=
r colored sheets of plastic or glass, depends strongly on their trans=
mission spectra and density ("darkness"). Unless your filters have b=
een carefully manufactured specifically for color mixing in introduct=
ory physics, you probably won't get the "textbook" result. =20

Vickie Frohne

-----Original Message-----
=46rom: Forum for Physics Educators on behalf of Robert Cohen
Sent: Sat 1/29/2005 10:51 AM
To: PHYS-L@LISTS.NAU.EDU
Subject: Re: Color (was LED mini-flashlight price break)
=20
I have several color films that I discovered in the lab. The blue is
really dark and looks purple next to cyan and looks blue next to the
violet. I assume the blue, red and green are very close to "just" bl=
ue,
red and green, because when I look at light through two together it i=
s
very dark.

Anyway, I also have yellow, cyan, violet and orange. I've found that
putting orange and cyan together I get a very nice green and putting
orange and violet together I get a very nice red. Orange and blue gi=
ves
black. Orange has very little effect when used with red or green.

Apparently, the orange film passes green and red equally. The yellow
filter appears to pass red more than green.

Why is this? Shouldn't my eyes interpret equal green/red as yellow, =
not
orange?

____________________________________________________
Robert Cohen; 570-422-3428; www.esu.edu/~bbq
East Stroudsburg University; E. Stroudsburg, PA 18301
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