Improvement on Newton’s original experiment

Improvement on Newton’s original experiment

The spectrum formed in Newton’s first experiment was impure. This resulted from the fact that it consisted of a series of circular coloured images all overlapping. Later Newton devised the arrangement shown in Fig. 25.2, which produced a fairly
pure spectrum. A converging lens L is placed so as to form an image I of a narrow slit S brightly illuminated by white light. A prism is then placed in the path of the light from the lens. Dispersion of the light on passing through the prism leads to the

Improvement on Newton's original experiment
Improvement on Newton’s original experiment

formation of a spectrum VR on a white screen. This consists of a series of coloured images of the slit all touching one another. If the slit is made narrow, overlapping is reduced to a minimum and the resulting spectrum is fairly pure.

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