Julia Bielaski
0163140
Lab Report #3
PH 232
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View Full DocumentObjective
:
The main goal of lab number three is to find the work function of an unknown material.
The system was made up of a phototube and light filters, hookup cables, voltmeter, electrometer,
a variable power supply, and a mercury lamp with housing and power supply.
In order to find
the maximum kinetic energy (which would eventually lead to the work function) we increased
the value of the voltage up to its stopping voltage.
At the stopping voltage, the kinetic energy is
equal to zero.
We repeated the process for seven different wavelengths and recorded the results.
Method
:
Equation 1: hv=K
0
+
φ
Note: if K
0
=0 then hv=
φ
φ
: Work function
Equation 2: K
0
=

e

V
s
Equation 1+2:

e

V
s
=hv +
φ
Equation 3: V
s
=(h/

e

)v

φ/
e

Table 1.1 Wavelengths and Uncertainties
Filter Number
Wavelength
(nm)
δλ
(nm)
on machine
435
50
on machine
546
50
on machine
577
50
46442
360
22
46432
407
50
46052
493
80
46436
520
46
Note: Distance between light source and filters is 1 meter.
•
Obtaining the initial frequency from the known initial wavelength:
f
i
=c /
λ
I
λ
i
=435.8nm
f
i
=(3.0x10
8
m/s) / (435.8x10
9
m)=6.88x10^14 Hz
f
i
=c /
λ
I
λ
=546nm
f=5.49x10^14 Hz
f
i
=c /
λ
I
λ
=577nm
f=5.20x10^14 Hz
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 Fall '10
 SCHULMAN
 Physics, Kinetic Energy, Power, Work, Light, lambda equals

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