Feb 2021

An Overview Of The Superposition Principle And Waves

February 9, 2021

In most cases in physics, when people discuss about the theory of superposition, they are talking about waves. Example of waves includes light, sound, water, and earthquake waves.

We all know that two objects cannot occupy the same space at the same time. But waves are energy travelling through a medium, so they behave differently than objects and can occupy the same space at the same time. This is why they do not collide but interfere with each other in a phenomenon which is known as superposition.

The superposition principle is one of those theories that sound much more complex than it actually is. Physics can be like that sometimes, but not to worry! Read on to learn more about what happens when two waves collide!

What is the principle of superposition?

The principle of superposition states that when two or more waves meet, the total displacement at any point is equal to the sum of the displacements that each individual wave would cause at that point.

What are the types of supposition waves?

When two waves interfere with each other, their effects add together to produce a total wave, also known as the resultant wave. We call it that because it’s the result you get when the waves are added up. There are 2 types of interference: constructive interference and destructive interference.

Constructive interference

Constructive interference happens when two interfering waves have a displacement in the same direction and they add up to result in a larger amplitude wave. The resulting amplitude is equal to the sum of the individual wave amplitudes. An example could be a load of individual voices in a crowd added together and thus, the whole crowd sound is louder than an individual’s voice.

Destructive interference

Destructive interference happens when two waves cancel one another out. This happens when the two interfering waves have displacemence in the opposite direction. The amplitude of the resulting wave is equal to the difference in amplitude of the individual waves.

Standing waves

Standing waves, also known as stationary waves, are a vibration of a system where some points remain fixed while others vibrate with the maximum amplitude. These waves are formed by the superposition of two or more travelling waves of the same frequency in opposite directions. For example, a long rope or slinky can be used to see the superposition principle in action. Have one person hold one end still, while the other person holds the opposite end and send waves down the slinky. The wave that travels along the slinky will bounce back once it reaches the other end, and collide into oncoming waves. At specific frequencies, you will see that the waves will no longer appear to travel, but instead form points that remain fixed.

Life will be very different if we don’t have stationary waves. Many technologies make use of stationary waves to take measurements such as distances. Stationary waves are also core to the music we listen to. When a person plays a note on the guitar, a standing wave is created on the string. When a person blows into a flute, a standing wave is created in the air inside the flute.


Many examples of wave superposition may not be directly visible in our daily life, but they are occurring everywhere. For example, when you sing in the shower, the reason you sound good is partly because of resonance, formed by superposition as the sound waves interfere with each other.

We hope you have gained a better understanding of the superposition principle and waves. If your exams are coming and you’re looking for A level or O level physics tuition, our tutors can help you understand the concepts and theories better! Sign up for physics tuition lessons today!

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