Question

Mention different parts of the spectrometer.

Answer 1

The spectrometer is an optical instrument used to study the spectra of different sources of light and to measure the refractive indices of materials. It is shown in following figure.

Spectrome

It consists of basically three parts. They are

1. collimator
2. prism table and
3. Telescope.

• Collimator:

1. The collimator is an arrangement to produce a parallel beam of light. It consists of a long cylindrical tube with a convex lens at the inner end and a vertical slit at the outer end of the tube.
2. The distance between the slit and the lens can be adjusted such that the slit is at the focus of the lens. The slit is kept facing the source of light.
3. The width of the slit can be adjusted. The collimator is rigidly fixed to the base of the instrument.

• Prism table:

1. The prism table is used for mounting the prism, grating etc. It consists of two circular metal discs provided with three levelling screws.
2. 2. It can be rotated about a vertical axis passing through its centre and its position can be read with verniers V₁ and V₂. The prism table can be raised or lowered and can be fixed at any desired height.

• Telescope:

1. The telescope is an astronomical type. It consists of an eyepiece provided with cross wires at one end and an objective lens at its other end.
2. The distance between the objective lens and the eyepiece can be adjusted so that the telescope forms a clear image at the cross wires when a parallel beam from the collimator is incident on it.
3. The telescope is attached to an arm that is capable of rotation about the same vertical axis as the prism table. A circular scale graduated in a half degree is attached to it.
4. Both the telescope and prism table is provided with radial screws for fixing them in the desired position and tangential screws for fine adjustments.