Now, I can show you more, namely, that the
colour of the so-called coloured object is entirely dependent on the
existence in the light of the special coloured rays which it radiates,
and that this scarlet paper depends on the red light of the spectrum for
the existence of its redness. On passing the piece of scarlet paper
along the coloured band of light, it appears red only when in the red
portion of the spectrum, whilst in the other portions, though it is
illumined, yet it has no colour, in fact it looks black. Hence what I
have said is true, and, moreover, that red paper looks red because, as
you see, it absorbs and extinguishes all the rays of the spectrum but
the red ones, and these it radiates. A bright green strip of paper
placed in the red has no colour, and looks black, but transferred to the
pure green portion it radiates that at once, does not absorb it as it
did the red, and so the green shines out finely. I have told you that
sodium salts give to a colourless flame a fine monochromatic or pure
yellow colour.
Pages:
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197