2. What is wave interference?
● A phenomena that occurs
when two waves interact
within the same medium.
● An simple example of this
would be if you threw two
rocks in a pond at the same
time near one another.
Circular waves would form.
These waves would
eventually meet each other
and “interfere”.
The boxed area highlights the region of
interference.
3. Terminology of wave interference
Source: Origin of the wave propagation.
Crest: The place on the wave with the maximum
value or displacement.
Trough: Occur between crests. The place on the wave
with the minimum value or displacement.
Super Crest: Wherever a crest meets a crest. This
creates Constructive interference.
Super Trough: Wherever a trough meets a trough.
The water experience great turbulence here. This
creates Destructive interference.
Crest and Trough meet: The water is very calm
because they cancel out one another.
Central maximum: Water will be very turbulent here.
In the diagram to the right this is represented by the
red line.
Wavelength: the distance between two crests.
Crest
(indicated by grey lines)
Trough
Super Crest Super Trough
Crest and trough
meeting
λ (wavelength)
4. Constructive vs. Destructive
Constructive Interference:
● points where crests meet OR
points where troughs meet
● Turbulence and increased
amplitude
Destructive Interference:
● where crest and trough meet
● Very calm water with no
amplitude
5. Nodal Lines
By marking all of the crest and trough interaction we learned on the previous slide we can see that a pattern begins
to form. These marked blue and red lines are called nodal lines. These nodal lines produce a fan shaped pattern.
Here we see the formation of constructive interference given by the red lines and destructive interference given
by the blue lines.
6. Using the paths or distance from each source we can find the initial wavelength that produced this pattern.
Equation of Path difference: abs(PS1 - PS2)= (n- ½)λ
Making sense of wave interference
S1 S2
P
7. Knowing the basics of wave interference will be
extremely helpful for future problems. The
information covered in this presentation will be
crucial in understanding more complicated examples
like the Young’s double slit experiment. Young’s
double slit experiment uses formula derived from the
formula you were introduced to in this presentation.
Summary
