3.13.4 Experimental procedures
(1)Aim the slit of the collimator at the light source of the sodium lamp.
(2)Loosen the brake screws of the telescope and vernier disk,and turn the stage and the telescope to the position 1 shown in Figure 3.13.10,and then rotate the telescope slightly to find out the light refracted by the prism.
Figure 3.13.10 Schematic diagram of measuring the minimum deflection angle(https://www.daowen.com)
(3)Turn the stage slightly(change the incident angle i1),and you will see the light moving with it.Change i1 and then make the light move to the direction with reducing δ(that is,to the direction of vertex A).The telescope moves with the light until the light begins to move in the opposite direction as the prism continues to rotate.The turning point of the reverse movement is the direction in which the light is emitted at the minimum deflection angle.Fix the locking screw of the stage and adjust finely the telescope to make the center vertical line on the reticule align with the spectral line.
(4)Write down the readings θ1 and θ2 of the two cursors.Remove the prism,but the stage keeps unchanged.Rotate and align the telescope which is expressed as position 2 in Figure 3.13.10 to the collimator to determine the position of the incident light,and then record the readings
and
of the two cursors.At this moment,the minimum deflection angle of the light is:
