It is used for quantitative light experiments. The collimator is fixed on the base and the telescope can be rotated. Concealed helical focusing is provided on the telescope and collimator tubes. The collimator slit has spring loaded jaws. The graduated prism table has a vernier attached which is fixed on the telescope arm. The prism table is adjustable with the help of 3 knurled screws and it has screwed holes for attaching prism & grating holder. It is plastic tubes and aluminium scale.