Experiment 9: THE TANGENT GALVANOMETER
PURPOSE:
In this experiment we will measure the magnitude of the horizontal component of the
Earth's Magnetic field by the use of an instrument called a tangent galvanometer.
INTRODUCTION:
A tangent galvanometer consists of a number of turns of copper wire wound on a hoop. At
the center of the hoop a compass is mounted. When a direct current flows through the wires, a
magnetic field is induced in the space surrounding the loops of wire. This magnetic flux is
designated by Bi . The strength of the magnetic field induced by the current at the center of the
loops of wire is given by Amperes law:
Induced Bi =
o N I
.
2R
where o is the permeability of free space and has the value of 4 x 10-7 N/A2, N is the number
of turns of wire, I is the current through the wire, and R is the radius of the loop.
When the wire loops of the tangent galvanometer are aligned with the magnetic field of the
Earth, and a current is sent through the wire loops, then the compass needle will align with the
vector sum of the field of the Earth and the induced field as shown in Figure 1.
Magnetic
North
Bresultant
B of Earth
Compass Needle
Direction

Bi
(induced)
Fig. 1
The horizontal component of the magnetic field of the Earth is easily calculated from the
following relation:
B of Earth =
- 24 -
Bi
.
tan 
SUPPLIES & EQUIPMENT:
Tangent galvanometer
Reversing switch
DC supply, 6 V
Ammeter
Ruler
Plywood board
Leads & connectors
Rheostat, 20 
PROCEDURE:
1. Set up the apparatus on a board between tables as shown in Figure 2. Be sure to orient the
loops exactly in the North-South direction. Orient the compass so that the needle is pointing
to zero degrees.
Rheostat
A
Reversing
Switch
Tangent
Galvanometer
5
10
15 Turns
Binding posts configuration
Fig. 2: Apparatus Wiring Diagram
2. Supply power to the 10-turns binding posts and adjust the rheostat until a deflection of 45 o is
indicated on the compass. Reverse the current to obtain a 45 o deflection on the other side of
the compass. Record the exact current for each deflection.
3. Sketch a vector diagram for the situation where there is a 45 o deflection. Calculate the
magnitude of the horizontal component of the Earth's magnetic field. The SI unit for B is the
Tesla (T). There are 104 gauss per Tesla.
4. Repeat steps 2 and 3 for a 63.5o deflection. What is the relationship between the Earth's field
and the field of the loop for this case? Draw a vector diagram.
5. Repeat the entire procedure for the 15-turns binding posts. What conclusion can you draw
about the magnetic field of the loop from this part of the experiment?
- 25 -
DATA SHEET: The Tangent Galvanometer
Data and Calculations table for 45o deflection
Number
Of Turns
Current
(A)
Deflection
Right
10
45o
15
45o
Left
Binduced
(T)
BEarth
(T)
Binduced
(T)
BEarth
(T)
Average
Vector diagram for above case
Data and calculations table for 63.5o deflection
Number
Of Turns
Current
(A)
Deflection
Right
10
63.5o
15
63.5o
Left
Vector diagram for above case
- 26 -
Average
Experiment 10: CAPACITIVE & INDUCTIVE REACTANCE
PURPOSE:
In this experiment we will study the effects of inductors and capacitors in a series
alternating current circuit. From the observation of these effects, the concepts of high pass and
low pass filters will be apparent.
INTRODUCTION:
In an AC circuit containing resistance and either inductance or capacitance, the resistive
effect of these circuit elements is called the inductive reactance X L and capacitive reactance XC
respectively. These reactances are given theoretically by:
XL = 2 fL,
XC =
1
2fC
.
(Unit is the ohm.)
These impedances are proportional to the frequency at which the circuit is driven. Experimentally,
we can obtain a value for these reactances from the following equation:
XL = VL/I
XC = VC/I
Since the voltages across the inductor and capacitor are out of phase with the voltage across the
resistor VR by 90o, it is necessary to add the voltages vectorially to obtain the voltage across
either the inductor or the capacitor:
VL =
Vs2

VR2 .
(where Vs = source voltage)
The current in the circuit is given by: I = VR/R
SUPPLIES & EQUIPMENT:

AC generator
Frequency counter
Digital voltmeter DVM, ACV 2-Volt range
Inductance coil, 10 mH
Composition resistor, 470
(yellow, violet, brown, silver)
Ruler & French curve
Decade capacitor box
- 27 -
f
V
BNC
Output
BNC
2 Wires
PROCEDURE:
Part
A.
Inductive Reactance
1. Set up the apparatus as shown in Figure 1.
L
Vs
R = 470
~
VR
Fig. 1
2. Set the function generator (Vs) to approximately 2 Volts and set the frequency to 1000 Hz.
(Check Vs with the DVM set at ACV, 2V and check the frequency with the frequency counter.)
3. Record the source voltage and the voltage across the resistor on the data table.
4. Determine
VL from VL = Vs2
I from

VR2
I = VR / R
XL from XL = VL / I
5. Repeat steps 2 through 4 for f = 1500 Hz to 4500 Hz in steps of 500 Hz.
6. Compare the experimental reactance with the theoretical reactance.
7. Plot XL versus frequency.
Part B: Capacitive Reactance
1. Repeat the above procedure only this time use a 0.5 F capacitor as the element instead of
the inductor.
- 28 -
DATA SHEET: Capacitive and Inductive Reactance
Data and Calculations Table 1: Inductive Reactance.
Frequency
f
(Hz)
Source
Voltage Vs
(V)
Voltage
Across
Resistor VR
(V)
Voltage
Across
Inductor VL
(V)
Current I
(A)
Inductive
Reactance
XL
()
Theoretical
XL
()
% difference
Current I
(A)
Capacitive
Reactance
XL
()
Theoretical
XC
()
% difference
1500
2000
2500
3000
3500
4000
4500
Data Table 2, Capacitive Reactance
Frequency
f
(Hz)
Source
Voltage Vs
(V)
Voltage
Across
Resistor VR
(V)
Voltage
Across
Capacitor VC
(V)
1000
1500
2000
2500
3000
3500
4000
4500
- 29 -
Experiment 11: THE OSCILLOSCOPE
PURPOSE: a) Introduce the principles of operation
b) Measure AC voltages and frequencies
c) Observe Lissajous Figures
INTRODUCTION:
The oscilloscope (shown schematically in Figure 1) is an essential instrument in the study
of AC signals and circuits.
Vertical Input
Amplifier
Filament
Electron Beam
Synchronizing
Voltage
Amplifier
Vo
Switch
Generator
Horizontal Input
Fig. 1. The Oscilloscope
HITACHI
OSCILLOSCOPE
A
B
D
E
C
F
H
G
J
I
K
L
O
M
N
P
Q
R
Fig. 2
A)
B)
C)
D)
E)
F)
G)
H)
I)
Power on/off and intensity
Horizontal position of both traces,
pull switch for 10X horizontal
Trigger setting for channel 2.
Beam focusing
Time per screen division = 1 cm
Knob making time/division variable.
Screen scale illumination.
x-y setting for Lissajous Figures.
Type of signal for channel 1.
J)
K)
L)
M)
N)
O)
P)
Type of signal for channel 2.
Channel trigger settings.
Channel 1, vertical amplitude
Chooses type of display for channels 1 & 2
Channel 2, vertical amplitude
Signal input for channel 1.
Vertical positioning of trace of channel 1.
Pull switch for 5X vertical.
Q) Vertical positioning of trace of channel 2.
R) Signal input for channel 2.
Pull switch for 5X vertical.
- 30 -
SUPPLIES & EQUIPMENT:
Hitachi dual trace oscilloscope V-550B
Function generator (F. G.) Simpson # 420
Digital voltmeter Digetec, model 2180
Power outlet strip
BNC to banana adaptor
1000  carbon resistor
Test leads as needed
Frequency counter,
Tenma, model # 72-460
PROCEDURE:
PART I: OSCILLOSCOPE SETUP
A. Adjustments to obtain trace:
1) Intensity -Low
2) Trigger
-Ext
3) Position -Center
4) Coupling -AC
5) Focus
-Sharp
6) Sweep
-1 msec/cm
7) Deflection -1 V/cm
knobs/lever: A,G
C
B, P, Q
I, J
D, G
E
L, N
Refer to Figure 2.
PART II: MEASURING AN AC (SINE WAVE) VOLTAGE
1. Set up the apparatus as shown in Figure 3.
OSCILLOSCOPE
Sweep Rate
Frequency
Counter
~
AC
1000
Power
Supply
(F.G. 1)
To Ch. 1 of Scope
and to DVM
E
Time / Div.
L Volts / Div.
Ch. 1
Digital
Voltmeter
ACV
Fig. 3
2. Adjust the function generator to 100 Hz at 6 V peak-to-peak.
3 Compute Vrms ( = 0.707 Vo).
- 31 -
4 Record the sweep rate in ms/cm and centimeter per cycle. From the oscilloscope trace,
estimate the number of centimeters per cycle
Sweep rate ________________ ms/cm
convert to _______________ s/cm
1 cycle spans _________________ cm
Calculate the period (time for 1 cycle)
Period ___________ s/cycle = (___________ s/cm) x (___________ cm/cycle)
5. Read the root mean square voltage from digital multimeter and compare to the root mean
square voltage estimated on the oscilloscope trace. See Fig. 4.
Voltage
(Volts)
Vo
Vrms = 0.707 Vo

Vpeak-to-peak
Time (sec)
-Vo
Fig. 4
6. Sketch a trace of the 200 Hz AC signal seen on the oscilloscope. Indicate V pp, Vo and Vrms
on the reticule in the data sheet.
PART III: LISSAJOUS FIGURES
1. Set up apparatus as in Figure 5.
2. Adjust function generator # 2 (F.G. 2) to the same frequency and voltage as function generator
# 1 (F.G. 1).
3. Observe lissajous figures when F.G. 2 frequency is 2, 3, and 4 times that of F.G. 1
4. Observe the lissajous figures when F.G. 1 frequency is 2, 3, and 4 times that of F.G. 2.
5. Sketch all lissajous figures.
~
1000
F. G. 1
To Ch. 1 of Scope
and to DVM
N
Input
O
Ch. 1
To Ch. 2 of Scope
and to DVM
R
Ch. 2
Fig. 5
- 32 -
1000
F. G. 2
~
DATA SHEET: The Oscilloscope
Data Table 1
Generator
Frequency
Vpeak-to-peak
(Volts)
(Hz)
Vo
(Volts)
Calculated Vrms
(Volts)
Vrms From Voltmeter
(Volts)
100
200
1000
Data Table 2
Frequency From Oscilloscope
Generator
Frequency
(Hz)
Sweep Rate
(msec/cm)
(cm/cycle)
Frequency From Counter
Period
(sec/cycle)
Frequency
= 1/ Period
(Hz)
Frequency From
Counter
(Hz)
Period From
Counter
(sec/cycle)
100
200
1000
Trace of AC signal.
Horizontal: 1 ms / cm
Vertical: 1 V / div.
Data Table 3: LISSAJOUS FIGURES
Channel 1
(horizontal)
Frequency 1
Channel 2
(vertical)
Frequency 2
(2 waves with the same amplitude and different frequency whole multiples.)
60 Hz
100 Hz
100 Hz
100 Hz
200 Hz
300 Hz
400 Hz
60 Hz
200 Hz
300 Hz
400 Hz
100 Hz
100 Hz
100 Hz
Sketch
Trace
- 33 -
Experiment 12: THE VISIBLE SPECTRUM
PURPOSE:
The wavelengths of electromagnetic waves in the visible range will be determined with a
diffraction grating.
INTRODUCTION:
A diffraction grating consists of a number of closely spaced parallel lines ruled on a glass
surface. It is a useful device for separating out the various wavelengths in a spectrum. It has the
same effect as a prism but with greater resolving power.
According to the theory of interference, the condition for constructive interference is given
by:  = n= d sin where  is the path difference,n is the order number, is the wavelength, d
is the slit separation and  is the diffraction angle.
 = n

d 
 = d sin 
 n = d sin 

and
Fig. 1
 =
d sin 
n
The diffraction grating spacing d will be determined with a helium-neon laser beam of 633
nm wavelength ().
L
x
tan  = L
White Light

x
Grating
d = n/dsin,
n = order number, 1,2…
L 
 = tan-1 x
Screen
Fig. 2
SUPPLIES & EQUIPMENT:
Helium-neon laser
Grating stand & holder
Large replica grating
Incandescent light source
Large cardboard
11 X 17 paper
Two-meter stick
2 ring stands
2 buret clamps
Laser safety goggles
- 34 -
Laboratory jack
One-meter stick
Masking tape
Color pencils
PROCEDURE:
PART A: DETERMINATION OF THE GROOVE SEPARATION d
1. Set up the grating and helium-neon laser. See Figure 3. Set the grating at exactly two meters
from the chalkboard (L = 2.00). Measure the distance x for the 1 st and 2nd order (n = 1 and 2)
bright fringes from the central spot. Determine an average value for the groove spacing d
from your data. The wavelength of the laser light is 633 nm.
xleft
0center
He-Ne Laser
xright
Lab Jack
Fig. 3
PART B: DETERMINATION OF THE WAVELENGTH RANGES FOR VISIBLE LIGHT
1. Set up the apparatus as shown in Figure 4, replacing the laser with the incandescent source.
2. Record L. Record xupper and xlower for the upper and lower limit of each color band, as shown in
Figure 4.
3. Calculate .
0th order
White
White-light source
Violet
Blue
Green
Yellow
Orange
Red
xupper (Violet)
xlower (Violet) = xupper (Blue)
Fig. 4
Color
Violet
Blue
Yellow
Green
Orange
Red
upper
400 nm
424 nm
491 nm
575 nm
585 nm
647 nm
lower
424 nm
491 nm
575 nm
585 nm
647 nm
700 nm
Reference: Handbook of Chemistry and Physics
- 35 -
DATA SHEET: The Visible Spectrum
Data Table A: Distance from grating to screen = L = 2.000 m
Wavelength
| xright|
(m)
n
| xleft|
(m)
tan 
xaverage
(m)

sin 
d
n
sin 
1
633 nm
2
Average value of d = ________________ nm
(1)  = d sin
Data Table B: L __________
Color
x
(m)
tan 

sin 

(nm)
xu
u
xl
xu
l
xl
xu
l
Green
xl
xu
l
Yellow
xl
xu
l
Orange
xl
xu
l
Red
xl
l
Violet
Blue
u
u
u
u
u
- 36 -
% difference
Experiment 13: REFLECTION AND REFRACTION
AT PLANE SURFACES
PURPOSE:
a) To verify the law of reflection.
b) To show by ray tracing, the position and orientation of the virtual image of an object placed in
front of a plane mirror.
c) To determine the refractive index of glass by ray tracing and application of Snell's law.
INTRODUCTION:
The law of reflection states that the angle of incidence i of light rays is equal in magnitude
to the angle of reflection r.
i
r
Fig. 1. Reflection
The law of refraction, Snell's law, states that:
n1 sin 1 = n2 sin 2.
Fig. 2. Refraction
where n1 and n2 are the refractive indices of two different mediums. The refractive index of a
medium is defined as the ratio of the velocity of light in air, c = 3.00 X 10 8 m/s, to its velocity in
that medium. The refractive index of air is 1.000. The refractive index of any medium can be
determined by measuring the angle of incidence, 1, the angle of refraction 2 and applying
Snell's law.
SUPPLIES & EQUIPMENT:
Cork board
Plate glass
Refraction cube
Plane mirror
11 X 17 paper
Ruler & protractor
Long common pins
Colored pencils
- 37 -
Wood block
Masking tape
PROCEDURE:
PART A: REFLECTION
1. Draw a straight line across the middle of the paper and then draw a triangle with vertices A, B
and C. Tape the mirror to a block and set it vertically on the line so that the reflecting surface
(back side) is on the line. The setup is shown in Figure 3 below:
Fig. 3
2. Place a pin at vertex A. From the right side of this triangle, look into the mirror for the image of
pin A in the mirror. Regard the image in the mirror as A. Place a pin R1 in front of this image,
A. Along your line of sight *, place another pin R2 in front of R1 so that A and R1 both appear
to be right behind it. Draw a line joining the points R 2 and R1 and extend this line to the mirror
surface. Remove pins R1 and R2.
* Make sure that your eye level and the pins are on the same plane.
3. Repeat the same procedure to the left side of the triangle. With pin A still in place, locate L 1 in
front of A and L2 in front of L1. Join points L1 and L2 and extend the line to the mirror surface.
Remove pin A.
4. Place a pin at B. Repeat steps 2 and 3 for points R B1 and RB2, LB1 and LB2. Extend lines
RB1 RB2 and LB1 LB2 to the surface of the mirror.
5. Place a pin at C, repeat steps 2 and 3 for point C.
6. Remove the mirror and extrapolate the lines until they intersect at A, B and C. Join points
A, B and C to reconstruct the mirror image (virtual). Fold the paper along the mirror line and
hold it against the light to see if the object ( ABC) and the image ( ABC) can be
superimposed on each other.
- 38 -
7. For the vertex A only, draw a line from vertex A to the point where the line R 1R2 meets the
mirror. Construct a normal to the mirror at this point. Measure the angles of incidence and
reflection with a protractor. See Figure 3.
PART A: REFRACTION
1. Using another sheet of paper, draw two straight lines perpendicular to each other. Measure
and draw the three angles 1, 2, and 3. Make your angles 15o, 30o and 45o respectively
from the normal. The setup is shown in Figure 4. Place the glass cube along the horizontal
line and trace the outline of the glass cube.
Fig. 4
2. Place pins A and R as shown in Figure 4. Use a locater pin L to line up A and R that are on
the 15o line. Pins L and R should be as close to the glass surface as possible. Repeat the
procedure for the 30o and 45o angles.
3. Measure the angle of refraction for each incident angle. Use Snell’s law to compute the index
of refraction of the glass for each incident and refracted ray. Average three suitable values
and report an average index of refraction for the glass. Look up the literature value of the
index of refraction for plate glass. Compare your result to this value.
DATA SHEET: Reflection and Refraction at Plane Surfaces
Your drawings are part of your data.
Incident angle
1 = 15o
2 = 30o
Angle of Refraction
Refractive Index of
glass (n)
n(average)
- 39 -
3 = 45o
Experiment 14: THE THIN LENS
PURPOSE:
The purpose of this laboratory exercise is to investigate the way in which the image
distance, object distance and focal length for a thin lens are related.
INTRODUCTION:
The lens equation which relates the object distance, d o, image distance, di, and the focal
length, f, for a glass lens is:
f
1
1 1


d o di f
Eq. 1
do
di
In this experiment, we will use an optical bench to align a lighted object, a lens and a
screen. Light rays from the object,
, which pass through the lens will form real images that can
be focused on the screen. Observations will be made as to the nature of the image, that is,
whether it is real or virtual, erect or inverted, and magnified or reduced. Image location can be
estimated with the use of ray diagrams.
Examples of ray diagrams for convex and concave lenses.
Object
Object
F
F
Real
image
F
Virtual
Image
Concave lens
Convex lens
SUPPLIES & EQUIPMENT:
Optical bench & accessories
Ruler
20 cm double concave lens
20 cm double convex lens
- 40 -
F
PROCEDURE:
1. Determine the focal length of the convex lens that you are using by mounting the lens in a
stand at a distance from a window. Adjust the distance from the lens to a paper screen until
the image of an object outside the window is in sharp focus. Deduce the focal length of your
lens by using equation (1), with do = ∞.
2. Mount the lens at the midpoint of the optical bench and mount the screen and object lamp on
opposite sides of the lens.
3. Place the object at a position that is somewhat greater than twice the focal length of the lens
(do > 2f). Move the screen until you get a sharp focus. Describe the characteristics of the
image. Record the image distance and the object distance. Calculate the image distance
using Eq. 1.
4. Repeat step 3 for the object at exactly twice the focal length (d o = 2f).
5. Repeat step 3 for the object at somewhere between twice the focal length and the focal length
(2f > do > f).
6. Repeat step 3 for the object at exactly the focal length (d o = f).
7. Place the object at a distance that is within the focal length. Look through the lens and
describe the nature of the image (do < f).
8. Replace the biconvex lens with one that is biconcave. Look through the lens at the object and
describe what you observe.
9. Calculate the image distance di for images seen through the biconcave lens using the lens
equation.
10. Calculate the image height hi using the magnification equation.
| M | = | - di / do| = hi / ho
hi = ho | di / do|
11. On the graph paper, draw ray diagrams to scale. Indicate the scale used.
1.0 cm = ________ cm
- 41 -
DATA SHEET: Thin Lens
A. Data for step 3: (do > 2f)
do = ______________
Focal length from step 1: _______________ m
Characteristics of Images
Real / Virtual
di = ______________ (Calculated)
di = ______________ (Measured)
Upright / Inverted
Enlarged / Diminished / No Image
B. Data for step 4: (do = 2f)
do = ______________
di = ______________ (Calculated)
di = ______________ (Measured)
Real / Virtual
Upright / Inverted
Enlarged / Diminished / No Image
C. Data for step 5: (2f > do > f)
do = ______________
di = ______________ (Calculated)
di = ______________ (Measured)
Real / Virtual
Upright / Inverted
Enlarged / Diminished / No Image
D. Data for step 6: (do = f)
do = ______________
di = ______________ (Calculated)
Real / Virtual
Upright / Inverted
Enlarged / Diminished / No Image
E. Data for step 7: (do < f)
do = ______________
di = ______________ (Calculated)
di = ______________ (Measured)
F. Data for step 8: f = -
Real / Virtual
Upright / Inverted
Enlarged / Diminished / No Image
cm
(do > f)
do = ______________
di = ______________ (Calculated)
hi = ______________ (Calculated)
Real / Virtual
Upright / Inverted
Enlarged / Diminished / No Image
(do = f)
do = ______________
di = ______________ (Calculated)
hi = ______________ (Calculated)
Real / Virtual
Upright / Inverted
Enlarged / Diminished / No Image
(do < f)
do = ______________
di = ______________ (Calculated)
hi = ______________ (Calculated)
Real / Virtual
Upright / Inverted
Enlarged / Diminished / No Image
- 42 -
RAY DIAGRAMS FOR CONVEX LENSES:
a.
c.
. .F
b.
. .
d.
F
. .
F
..
F
Virtual Image
.
e.
.F
RAY DIAGRAMS FOR CONCAVE LENSES:
a.
. .F
b.
c.
. F.
d.
. .
F
e.
. .F
- 43 -
. .F
No Image
Experiment 15: ATOMIC SPECTRA
PURPOSE:
The purpose of this experiment is to measure the wavelengths of light emitted by atoms of
different elements.
INTRODUCTION:
The electrons of gases can be raised to excited states if the atoms of the gas absorb
specific quanta of energy. The electrons are said to have been raised from their ground state to
higher energy levels. When these electrons fall back to the ground state or to another lower level,
light is emitted. These photons have unique wavelengths corresponding to the difference in
energy between the two states of the electron as it falls.
In this experiment, high voltage supplies the energy to the atoms in the gas discharge tube.
The electrons are excited and fall to a lower state almost immediately. The mixture of light
produced can be separated using a diffraction grating and then the wavelength can be calculated
from the equation = d sin.
SUPPLIES & EQUIPMENT:
Spectrum tube power supply
2 One-meter sticks
Grating holder & stand
Ar, He, H Spectrum tubes
2 Buret clamps
Small reading lamp
2 ringstands
Grating
PROCEDURE:
1. Set up the apparatus as shown in Figure 2.
2. Adjust your eyes in a position such that you can locate the first order spectral lines.
3. Determine the x and L for each spectral line for argon, helium and hydrogen
L 
4. Determine tan  = x and  = tan-1 x .
L
5. Determine the wavelength,  of the spectral lines. The grating has 600 grooves per millimeter.
The grating constant, d, is the distance between the grooves on the grating. For our gratings,
1
d=
in units of nanometers.
600 000
6. Compare these wavelengths with the known spectral line values given.
- 44 -
e
1
+V
Gas
Discharge
Tube
Photon
Emission
e
2
e
V
3
Fig. 1
st
1 Order
Spectral
Lines
1 = d sin 1
2 = d sin 2
3 = d sin 3
 1,  2,  3
Light Rays
Gas Discharge
Tube
Meter
Stick
Virtual Image of
Spectral Line
x
Grating
Line Spectrum of this gas
Displayed on screen or
eyes

L = 1 meter
Eye
tan  = x/L   tan1(x/L)
Fig. 2
Selected spectral line wavelengths (in nm, See Handbook for complete description)
Helium
Red
Yellow
Green
Blue
Violet

668 nm
588 nm
502 nm
447 nm
403 nm
Argon
Red
Orange
Green
Blue-Violet

Hydrogen
697 nm
642 nm
523 nm
452 nm
- 45 -
Red
Turquoise
Purple
Violet

656 nm
486 nm
434 nm
410 nm
DATA SHEET: Atomic Spectra
Data Table 1: Argon
Line Color
Red
x (right)
(m)
x (left)
(m)
x (average)
(m)
Orange
Green
Blue


(nm)
 (known)
(nm)
% difference
Data Table 2: Helium
Line Color
x (right)
(m)
x (left)
(m)
x (average)
(m)
Red
Yellow
Green
Blue
Red
Blue-Green
Purple
Violet


(nm)
 (known)
(nm)
% difference
Data Table 3: Hydrogen
Line Color
x (right)
(m)
x (left)
(m)
x (average)
(m)


(nm)
 (known)
(nm)
% difference
- 46 -
Experiment 16: RADIOACTIVITY
PURPOSE:
To learn about the operation and the use of a geiger counter in the detection of radiation.
INTRODUCTION:
The Geiger Counter
Ion – Electron Pair
+
Ionizing
Radiation
-
Output to Counter
CPM
+
Optimum voltage is about 50 V the knee.
Avalanch Region
Knee
Plateau Region
Voltage
SUPPLIES & EQUIPMENT:
Geiger counter
Geiger tube
DATA SHEET: Radioactivity
Radiation measurements at optimum voltage ______________ V
Counts per 30 seconds
Front of Room
Near Door
Near Window
Back of Room
Near Door
- 47 -
Counts per minute
DEMONSTRATION LABORATORY ASSIGNMENT
INTERFERENCE
DIFFRACTION
POLARIZATION
TOTAL INTERNAL REFLECTION
COLOR PERCEPTION
PIN-HOLE CAMERA
Part I
There are nine lab stations that will serve to demonstrate some interesting optics
phenomena.
1. Soap bubble.
2. Hologram - car - interference
3. Optical flats - air gap - interference
4. Color Box - color addition and subtraction
5. Michelson's interferometer - interference pattern
6. Single slit diffraction - positive and negative slit
7. Polarized light - water surface - Brewster's angle - polarization
8. Total internal reflection--rainbow and fiber optics
9. Pin-hole camera
View the demonstration at each lab station, and write a paragraph describing your
observations and explaining the principles behind each demonstration.
Part II (Extra credit 10 pts.)
Construct a diffraction (pin-hole) camera.
Apparatus Notes:
1. Soap bubble: 1 part glycerin, 4 parts clear detergent, 10 parts water. Specify position of parts
of setup with masking tape on table.
2. Hologram: Diffuse sodium light with ground glass screen to prevent glare. Use black shield
and black paper underneath.
3: Optical flats: Diffuse sodium light with ground glass screen to prevent glare. View from onehalf to one meter away.
4. Color Box: Put out overhead projector with cardboard cover pieces also.
5. Michelson's interferometer: Put screen at least 2 m away.
6. Single slit diffraction - positive and negative slit multiple slits. Project on blackboard across
room. Use 2 pieces of paper 1' x 2.5' for screens.
7. Polarized light: Use circular adjustable polaroid holder. Use blue battery charger set at 6V and
12 V Pasco lamp.
8. Total internal reflection: Use large (8") crystallizing dish from chemistry. Place screen about a
meter away. Use slit opening over lamp. Use a red battery charger set at 12V and 12 V
Pasco lamp. Shield apparatus from stray light. Use lab jack for laser.
9: Pin-hole camera
STATION #1
THIN FILM
LIGHT
INTERFERENCE
PATH DIFFERENCE
IMPORTANT
Soap
Solution
BRIGHT FRINGE
WHEN IN STEP
STATION #2
HOLOGRAPHY
INTERFERENCE
Hologram
of Car
Sodium
Lab Jack
Lamp
STATION #3
OPTICAL FLATS
AIR GAPS
INTERFERENCE
View From Distance
Microscope Slide - Not Very Flat
Sodium
Lamp
Optical Flats -- Very Flat
STATION #4
COLOR BOX
COLOR ADDITION:
Color addition by
the mixing of
colored lights.
When three
projectors shine
red, blue, and
green light on a
white screen, the
overlapping parts
produce different
colors. The
addition of the
three primary
colors produces
white light.
COLOR SUBTRACTION:
LIGHT SOURCES
COLOR ME
RED
COLOR ME
MAGENTA
COLOR ME
Y ELLOW
PLEASE
DON'T
COLOR ME
COLOR ME
COLOR ME
BLUE
FILTERS
CY AN
COLOR ME
GREEN
STATION #5
MICHELSON'S
INTERFEROMETER
Laser Light Source
Half-silvered mirror
Movable Mirror
Screen 2 meters Away
INTERFERENCE
PATTERN
Compensator
Fixed Mirror
STATION #6
DIFFRACTION
MULTIPLE SLIT (4 Slits)
0.5 mW He-Ne Laser
Paper Screen
on Blackboard
SINGLE SLIT
A. SLIT
+ SLIT
0.5 mW He-Ne Laser
B. HAIR - SLIT
STATION #7
POLARIZATION :
UNPOLARIZED
WHITE LIGHT


POLARIZED
LIGHT





POLAROID
#1 =
POLARIZER
POLARIZATION BY REFLECTION:
qB
Air
Glass


WATCH
THIS



POLAROID
#2 =
ANALYZER


AS YOU
ROTATE THE
ANALYZER
STATION #8
TOTAL INTERNAL REFLECTION:
RAINBOW AND FIBER OPTICS
WATER
DROPS
SUNLIGHT
40 O
VIOLET
RED
VIOLET
RED
42 O
Translucent white
paper 1 m away
will show rainbow
on opposite side
White light source
Large Crystallizing dish with
very dilute unflavored gelatin
1:100 ?
STATION #9
PIN-HOLE CAMERA:
Source
Inverted image on
frosted glass screen