Light source used in N.P.L. type of flatness interferometer - Metrology & Quality Control

Q.  Which type of light source is used in N.P.L. type of flatness interferometer?
- Published on 07 Aug 15

a. Mercury vapour lamp
b. Cadmium lamp
c. Both a. and b.
d. None of the above

ANSWER: Mercury vapour lamp

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    Discussion

  • Sravanthi   -Posted on 26 Oct 15
    - Mercury vapour lamp is used in N.P.L. type of flatness interferometer as a source of light.

    - This light is passed through a green filter and removes all colors except monochromatic light. This monochromatic light has wavelength of 0.5 micron.

    - In Pitter NPL Gauge interferometry, cadmium or mercury lamp is used as a light source.

    - Mercury light source gives 2 yellow, 1 green and 1 violet light.

    - Cadmium light source gives 1 red, 1 blue, 1 violet and 1 green light.

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