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Interference of two Circular or Spherical Waves
Lesson Plan
Eleni Kyriaki
Target group
Secondary Level students – Age group of 16 - 17 years old
Target’s group required background
Oscillation – Oscillation Amplitude – Period - Frequency
Wave – Wavelength
Superposition Principle
Pulse Addition [3]
Related Historic Experiments
Young Interference Experiment
Objectives
1. To apply the Superposition Principle in waves
2. To work on the pattern derived from the experiment in order to find the constructive
and destructive points of the elastic medium
3. To work with the set of equation and find the same pattern (explore using
simulations)
4. To experiment with water, sound and light waves in real or web experiments
Didactic Approach
The phenomenon of the interference of two Circular or Spherical Waves is quite
complicated. You need to demonstrate static pictures, simulations and real or web
experiments to give an accurate picture of the phenomenon to your students.
The students must realize that to explain the complicated patterns you have to work point
by point on the elastic medium. To draw the correct conclusions you need precision,
imagination and good mathematical background.
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Lesson Plan
1st Lesson
Step 1 (10 min)
It is always good if you can start your lesson with a real experiment, if possible. If not, you
can use a static picture or a first demonstration of the simulation program (virtual
experiment).
Step 2 (20 min)
Then, it is useful to draw on the blackboard the product of the interference of two Circular
or Spherical Waves of the same wavelength derived by two sources oscillating with the
same amplitude the same face. I choose an easy drawing taking the distance of the
sources 4 times bigger than the wavelength. Examining the result in 4-5 points on the
“elastic medium” is enough; the students must notice that the difference of the distances
from the sources is related to the constructive and destructive result at each point.
Step 3 (10 min)
Give the opportunity to the pupils to work in small teams with the simulation program.
Worksheets that encourage them to try out different values of sources distance and
wavelength will help them observe and explore.
Step 4 (5 min)
Conclusions
2nd Lesson
Step 1 (5 min)
Repeat the demonstration of
the simulation – Discuss the
conclusions from the previous
lesson
Step 2 (15 min)
Next, the teacher presents the
theory which explains the
phenomenon and the set of
equations.
Step 3 (5 min)
The teacher demonstrates the
simulation program; it must be
Figure 1: The interference of waves demonstrated by Walter Fendt's
applet
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pointed out that the simulation is based on the equations.
Step 4 (15 min)
Exercises
Step 5 (5 min)
Conclusions
Resources
[1] The Xplora-Knoppix DVD which is distributed from the Xplora repository
http://www.xplora.org/ww/en/pub/xplora/library/software/xplora___dvd_knoppix__m
ake_sci.htm
[2] Walter Fendts JAVA applets http://www.walter-fendt.de/ph14e/interference.htm
[3] Pulse Addition http://physics.ham.muohio.edu/waveapplets/pulseadd.htm
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