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ASNT Level III- Visual & Optical Testing

My Level III Self Study Notes

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1.3.2 Light Sources<br />

The light source for visual tests typically emits radiation of a continuous or<br />

noncontinuous (line) spectrum. Monochromatic light is produced by use of a<br />

device known as a monochromator, which separates or disperses the<br />

wavelengths of the spectrum by means of prisms or gratings.<br />

Less costly and almost equally effective for routine tests are light sources<br />

emitting distinct spectral lines, These include mercury, sodium and other<br />

vapor discharge lamps. Such light sources may he used in combination with<br />

glass, liquid or gaseous filters or with highly efficient interference filters, for<br />

transmitting only radiation of a specific wavelength.<br />

Keywords:<br />

Continuous spectrum<br />

Non-continuous spectrum-Monochromatic light<br />

Monochromator used prisms or grating<br />

Charlie Chong/ Fion Zhang

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