Wave interference occurs when two waves superimpose, or overlap, in the same medium. This can result in a resultant wave with either constructive or destructive interference. Constructive interference occurs when wave peaks and troughs align, creating a resultant wave with greater amplitude. Destructive interference happens when wave peaks and troughs cancel out, resulting in a wave of lower amplitude. Whether interference is constructive or destructive depends on the phase difference between the overlapping waves.

2. WHAT IS WAVE INTERFERENCE AND HOW
DOES IT OCCUR?
• Wave interference is the physical phenomenon of the formation of a resultant
wave that either has a higher and lower amplitude than the waves that
caused it.
• It can be categorized into two different types of interference: constructive and
destructive.
• Wave interference occurs when two waves with different phase constants, but
the same amplitude, frequency, wavelength and direction undergo
superposition.

3. BUT WAIT… WHAT IS SUPERPOSITION?
• Superposition happens when two or more waves are in the same medium at
the same time.
• Essentially, it is the process that happens when two waves run into each
other and are combined.
• This process forms a resultant wave that either has constructive or
destructive interference, as touched on in the previous slide.

4. …AND WHAT ABOUT A RESULTANT WAVE?
• A resultant wave is the wave that is formed by the adding/combining of the
two or more waves during superposition
• The resultant wave is key to the phenomenon of wave interference and helps
us to identify what type of interference is happening
• The displacement of a resultant wave can be calculated by adding together
the displacements of each individual wave that made it
• This can be shown with the equation:
D(x,t) = D1(x,t) + D2(x,t) + D3(x,t) … Dn(x,t)

5. OKAY… SO WHAT’S THE DIFFERENCE
BETWEEN CONSTRUCTIVE AND
DESTRUCTIVE INTERFERENCE?
• Constructive interference of waves happens when the resultant wave that is
formed has a GREATER amplitude than that of the superposed waves that
formed it.
• On the other hand, destructive interference of waves happens when the
resultant wave that is formed has a SMALLER amplitude than that of the
superposed waves.
• Constructive and destructive interference happen based on the phase
constants that the superposed waves bring to the table.

6. PHASE CONSTANTS AND WAVE
INTERFERENCE
• As explained in a previous slide, wave interference happens when two or
more waves with different phase constants are combined to make a resultant
wave.
• If the difference in phase constants between the two waves is either zero or a
multiple of 2π, then it is thought to be in phase and therefore will result in
constructive interference because the waves are “helping” each other.
• If the difference in phase constants between the two waves is an odd multiple
of π, then it is thought to be out of phase and therefore will result in
destructive interference because the waves are “destroying” each other.

7. EXAMPLES OF CONSTRUCTIVE AND
DESTRUCTIVE WAVE INTERFERENCE
• We can apply our knowledge of constructive and destructive wave
interference to explain real life scenarios
• Take sound waves for example:
• We can tell that there has been destructive interference when a sound gets
quieter or there is no sound
• And that there has been constructive interference when a sound gets louder

8. EXAMPLES OF CONSTRUCTIVE AND
DESTRUCTIVE WAVE INTERFERENCE
• The next couple slides will show examples of constructive and destructive
wave interference through the use of diagrams.

9. EXAMPLES OF CONSTRUCTIVE AND
DESTRUCTIVE WAVE INTERFERENCE

10. EXAMPLES OF CONSTRUCTIVE AND
DESTRUCTIVE WAVE INTERFERENCE