Gordon Hansen, age 16, of Asbury Park, N.J., for his question:

CAN YOU EXPLAIN THE RAMAN EFFECT?

The Raman effect is a change in frequency observed when light is scattered in a transparent material. This phenomenon was discovered by an Indian physicist named Sir Chandrasekhara Venkata Raman in 1928.

When monochromatic light, such as that obtained from a laser, is passed through a transparent gas, liquid or solid and is observed with the spectroscope, the spectral line ordinarily produced by the light has associated with it lines of longer and of shorter wavelength, called the Raman spectrum.

These lines are caused by photons losing or gaining energy by elastic collisions with the molecules of the transparent substances.

The Raman spectrum of a particular spectral line varies with the nature of the material that scatters the light. The Raman effect has practical importance in spectrographic chemical analysis and in the determination of the structure of molecules.