We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
THE CHEMICAL ACTION OF LIGHT 39
Light waves are not a fiction. Not only has their existence been ascertained, but their size has been determined. The latter is extremely minute, but nevertheless is susceptible of measurement.
Analogy between Waves of Light and Waves of Sound. — The waves of sound and the waves of light have therefore a certain analogy ; and as there are different notes in music, so are there different colours in light. The number of notes is great. The simplest piano now has six or more octaves, and there are other tones below and above these. But the number of colours is small ; only seven of them can be distinguished — red, orange, yellow, green, blue, dark blue, and violet — the well-known colours of the rainbow. The painter, indeed, contents himself with three ground tints — yellow, blue, and red. All the others are the result of their mixture ; and the large scale of colour of the painter consists not of simple tones of colour, but of what may be called chords of colour.
The deep tones of music are caused by few undulations occurring per second, the higher tones by more. For example, an a string makes 420 vibrations in a second, the a an octave lower makes 210, the A 105.
In light, red is the colour which is produced by the slowest vibrations ; it is the lowest tone in colours, and violet is the highest, being produced by vibrations nearly twice as rapid as red. With regard to tones, we know that they all spread with equal rapidity in the air ; if this were not the case, a piece of music would be heard in the distance as a most disagreeable discord.
It is the same in the kingdom of light — the colours, without exception, are propagated through the ether with equal rapidity, the red as fast as the violet. But, whilst sound passes over only 1100 feet in the second, light traverses about 186,000 miles in the same time, and the deepest colourtone — red — requires in a second 420 billion of vibrations — that is to say, a million times