EXPERIMENT 4—3
93
according to the strength of the light source (try a 5 watt clear 110
volt lamp 2 feet away) until the temperature lowers to somewhere
between —70°. and ——140° C., when a sudden drop in the current
Will be observed.
(3)’ With a light source consisting of a 100 watt
lamp bulb about 4: feet away, expose the cell continuously and
observe the gradual decrease of current output, i.e., the fatigue
effect.
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EXPERIMENT 4—3
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THE SPECTRAL DISTRIBUTION CURVE OF A
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PHOTOELECTRÏC CELL
Âpparqtus.+In order to secure various monochromatic beams
of light whose wave—lengths are distributed over the visible
spectrum, use One of the three following methods: the rst is comparatively inaccurate but is cheap, thelast, much better but
expensive._
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‘
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(1) A projection lantern With lenses removed, and having a
400 to 500 watt lamp which sends light to the photo—cell through
the lters listed below.
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TABl.E
4—1.—Soivm FILTERS\ FOR PHOTOELECTRIC WORK
_
.
Corhing 5 X 5 cm.
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; Effective Wave—length
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_
…
1n angstroms
#
.“.'..‘-.
.
-/9
8000
H R
# 245,_pluszklo # 397 ..… .
,.
_‘j' 6500
Pl‘%$
“ÎîÏ5500
,
’
4500 f
.
"
RedpurleCorexA#986plu‘sAklo
":”;
3500
—
Theltèrssh@uldelocatedpreferablyJust1nfmntoftheœ
aîsanystrayorseatteredhghtTheefïect1vewavelengthshsœd : ‘
.
œmmat1®nS@flensesandPsmsmaY@bV10u31ybeusedthe
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