Slides from Pasco optics kit: A) Light source aperture #9118 B) Variable diaphragm #9117 C) 48 mm convex lens #9133 D) 18 mm convex lens #9132
Set up as shown. Line #9118 up so that the beam goes through on of the apertures. Adjust the top knob on #4 and the sensitivity knob on #3 until you get about a half-scale deflection on #3.
Slowly close the diaphragm watching the intensity scale of the photometer. With proper adjustment of positions of the components you should see the intensity gradually decrease as you close the diaphragm. But watch carefully – a one point needle will rise, indicating an intensity increase.
Caution: Don’t bend the fiber optics cable – it is sensitive to flexing.