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Microcosmology : Atom
but on its colour. Thus each photon of a given colour, say, green, has a certain amount of energy. Reducing intensity only reduces the number of photons, but each green photon has the same amount of energy. This brings us to the problem of colour.
Newton had discovered that if sunlight passes through a triangular-shaped piece of glass, one of the most beautiful phenomena occurs. From the other side of the glass comes not white light but every colour in the rainbow from red to violet with orange, yellow, green, blue, and indigo in between. This display of colours is called visible spectrum. When white light, which is a mixture of different colours, passes through prism, different colours are bent by different amounts-red the least, violet the most. Each colour has its own specific wave-length and frequency. The wave-length of red is longest while that of violet is shortest.
All the colours of visible light (together with infra-red and ultra-violet radiations) represent only a small portion of a band of radiations from high-energy X-rays to low-energy radio waves. The higher the energy, the shorter is the wave-length. Thus, high frequency light such as violet has a short wave-length and a high energy; low frequency light such as red has a long wave-length and a low energy. Velocity is the product of wave- length and frequency. The velocity of all electromagnetic waves -- lights of all colours radio-waves, X-rays, and all the other forms of radiation -- is always 1.86.000 miles per second (i.e.3,00,000 kilometers per second). This constant speed of light is usually represented by the letter "c".
In the beginning of the 20th century, thus, there were two successful theories :
(1) Newtonian mechanics, and
(2). Maxwell's electrodynamics; the Newtonian monopoly of being the basis of all physics was destroyed.
B. STRUCTURE OF ATOM
For fully understanding the structure of matter, we have to descend from the macroscopic to the microscopic level This has to be done in two stages --first, at the atomic level and second, at the subatomic level.