Using A Projection Microscope With The Millikan Oil Drop Apparatus - PASCO AP-8210A Instruction Manual

M i l l i k a n O il D r o p A p p a r a t u s
Suggested Procedure for Computation of the Charge of an Electron:
1. Use the following equation to calculate the radius, a, of the oil drop:
2. Substitute the radius, a, from the above equation to find the mass, m, of the oil droplet:
3. Substitute m from the calculation above into the equation for computing the charge of an electron:
Using a Projecting Microscope with the Millikan Oil Drop Apparatus
To demonstrate Millikan's experiment for an entire classroom on a TV screen or computer monitor, use a project-
ing microscope such as the Ken-A-Vision VideoFlex Microscope (PASCO Model SE-7227).
Procedure
1. Put a white paper screen in the droplet viewing
chamber to reflect more light:
a. Prior to focusing the viewing scope (see Equipment
Setup section, Aligning the Optical System), place
a white paper screen in the droplet viewing chamber
as illustrated in Figure 10.
b. Proceed with step 1 of Aligning the Optical System.
2. Align and focus the projecting microscope:
a. Set up the projecting microscope as directed in the
manufacturer's instructions.
b. After completing the setup and focusing of the Mil-
likan Oil Drop Apparatus on the oil droplets, care-
fully slide the eyepiece of the projecting microscope
over the eyepiece of the Millikan Apparatus.
c. Focus the projecting microscope as directed in the
manufacturer's instructions.
12
9v
2
b
 
----- - ---------- -
a = +
 
2p 2g
4
3
-- - a 
m =
3
9v
2
4 b
 
-- - 
----- - ---------- -
m = +
 
3 2p 2g

mg v + v
f
--------------------------- -
q =
Ev
v
9v
2
4 b
 
f
-- - g ----- - ---------- -
q = +
 
3 2p 2g
2. Place the
paper screen so
the light path is
not blocked and
so the light is
reflected towards
the viewing
scope.
012-13093B
b
f
----- -
–
2p
3
b
f

----- -
–
2p

r
3
v + v
b
f r
----- -  -------------- -
–
2p Ev
f
paper
screen
cross-section of
the droplet
chamber housing
viewing
scope
Figure 10: Place a white paper screen in the
droplet viewing chamber.
E q u i p m e n t
1. Cut a 32 by 6
mm strip of white
paper and bend
back tabs of 6 by
6 mm.
spacer
light path
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