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a) |
A table (5) with threaded holes allowing one to screw components on the surface. |
b) |
A variable intensity light source (4), i.e. a mercury vapor lamp with a collimated (nearly parallel) output beam. |
c) |
A diffraction grating (3) which, upon reflection, splits the white beam into multiple, single-color beams, one for every spectral line of the spectrum of mercury. |
d) |
A vacuum cell (1) containing two metal plates (or electrodes), the first one with a hole allowing the incoming light beam to strike the other. The electrodes are connected to two wires allowing one to put a voltage and to measure the current flowing between them. A schematic drawing of the circuit (16) is shown on the table. |
e) |
A distance-controlled supporting system (2) allowing one to rotate either only the grating (3) or both the lamp (4) and the grating. |
Figure 1 Screeshot of the simulated apparatus. |
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More precisely, lhe
controllers allow one to (left to right) |
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f) |
Change the ambient room lighting (7). In the screenshot, the lighting has been reduced by about two thirds. |
g) |
Change the lamp intensity (6). |
h) |
Rotate either the grating only (8) or the base supporting both the grating and the lamb (9). |
i) |
Change the voltage (10) between the electrodes in the celle (voltage can be either positive or negative). |
j) |
Read, on a digital display (11), the value (in volts, V) of the voltage between the electrodes. |
k) |
Read, on a digital display (12), the value (in picoamperes, pA, i.e. 10-12 A ) if the current flowing between the electrodes. |
l) |
Measure the same quantity with a multiple-scale analog picoammeter (14); six different scales are available (15) with maximum deviation of the needle between 0,001 and 100 pA. |
m) |
Change the cell for another with electrodes made of a different metal. Four different metals are available (13). |
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