Tuesday, 1 September 2009

Raman Effect

Sometimes a rainbow appears and delights our eyes. We see in it shades of red, orange, yellow, green, blue, indigo and violet. The white ray of the sun includes all these colors. When a beam of sunlight is passed through a glass prism a patch of these *color- bands are seen. This is called the spectrum. The Spectro- meter is an apparatus used to study
the spectrum. Spectral lines in it are characteristic of the light passing through the prism. A beam of light that causes a single spectral line is said to be monochromatic.

When a beam of monochromatic light passes through a transparent substance (a
substance which allows light to pass through it), the beam is scattered. Raman spent a long time in the study of the scattered light.. On February 28, 1928, he observed two low intensity spectral line corresponding to the incident mono- chromatic light. Years of his labor had borne fruit. It was clear that though the incident light was monochromatic, the
scattered light due to it, was not monochromatic.Thus Raman's experiments discovered a phenomenon which was lying hidden in nature.

The 16th of March 1928 is a memorable day in the history )f science. On that day a
meeting was held under the joint auspices of the South Indian Science Association and the Science Club of Central College, Bangalore; Raman was the Chief Guest. He announced the new phenomenon discovered by him to the world. He also acknowledged wit h affection the assistance given by K.S. Krishnan and Venkateshwaran, who were his students.

The phenomenon attracted the attention of research workers all over the world. It
became famous as the 'Raman Effect'. The spectral lines in the scattered light were known as 'Raman Lines'.

Is light wave-like or particle-like? This question has been discussed from time to time by scientists. The Raman Effect confirmed that light was made up of particles known as 'photons'. It helped in the study of the molecular and crystal structures of different substances.



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