(1) Light the mercury lamp, using a regulated voltage source (if possible), and leave it to warm
up for 5 minutes.
(2) Place the ground quartz plate above slit S1.
(3) Turn on the spectrophotometer power supplies, and set the photomultiplier sensitivity
control for minimum sensitivity.
(4) Place the mercury lamp over the inlet window to illuminate the ground quartz plate.
(5) Set the wavelength selector rod for SHORT wavelengths and turn the spectro-photometer
dial to 300 degrees (or as far as it will go in the Counter-clockwise direction). (This means
that effectively only slit S2 is open and that the microammeter deflection will be a measure
of the light passing through it).