Question

Explain the preliminary adjustments of the spectrometer.

Answer 1

The following adjustments must be made before doing the experiment using a spectrometer.

1. Adjustment of the eyepiece:
   The telescope is turned towards an illuminated surface and the eyepiece is moved to and fro until the cross wires are clearly seen.
2. Adjustment of the telescope:
   The telescope is adjusted to receive parallel rays by turning it towards a distant object and adjusting the distance between the objective lens and the eyepiece to get a clear image on the cross wire.
3. Adjustment of the collimator:
   The telescope is brought along the axial line with the collimator. The slit of the collimator is illuminated by a source of light. The distance between the slit and the lens of the collimator is adjusted until a clear image of the slit is seen at the cross wire of the telescope. Since the telescope is already adjusted for parallel rays, a well-defined image of the slit can be formed, only when the light rays emerging from the collimator are parallel.
4. Levelling the prism table:
   The prism table is adjusted or levelled to be in a horizontal position by means of levelling screws and a spirit level.