Turn off the lamp immediately after the experiment is over. Unplug the electrical outlet. Do not remove the eyepiece from the telescope or touch the eyepiece lens. Present knowledge of atomic physics grew out of simple spectroscopic experiments such as the one you will perform in this lab. Light has been a fascinating subject of studies for many years and only partially understood even at present.
Light is also one of our most powerful tools for probing nature.
The atoms of a substance when sufficiently disturbed, emit a unique set of wavelengths of light. The angular deviation depends on the medium under consideration and also on the wavelength of light. The speed of light in a medium depends on wavelength. The change in the index of refraction with wavelength, is called dispersion. This ray from the collimator passes through a prism placed at the center of the circular table and reaches the telescope for viewing.