11 Superposition

Principle of Superposition

Observe and explain - Can you explain this phenomenon?

A simulation on what could possibly happen can be found here.

Superposition of pulses

    Stationary wave

    Formation of stationary waves

    When two progressive waves of same amplitude and same frequency travelling with the same speed in opposite directions are superposed, a stationary or standing wave is formed.

    Wave function plotter 

    • Remix of simulation by Wee Loo Kang who remixed from Wolfgang Christian and Francisco Esquembre
    • Download simulation here
    • Explore what happens when the conditions of stationary formation are not met

    Wave function plotter for longitudinal wave

    • Download simulation here
    • Show the relation of displacement position graph with actual particles oscillations

    Stationary waves questions that can be answered by the simulation

    1. Some musical instruments rely on stationary waves on strings in order to produce sound. Suggest why strings made of different materials or with different diameters are sometimes used.
    2. In order to investigate stationary waves on a stretched string, a student set up the apparatus below. Explain why it is necessary to adjust either the vibrating length of the string or the frequency of the vibrator in order to obtain observable stationary wave.

    Huygen's principle

    A flash animation explaining Huygen's principle.

    Two sources interference

    Simulation to illustrate two sources interference (download simulation here) of a ripple tank demonstration. You may investigate:

    • Meaning of path difference
    • constructive/destructive interference due to path difference
    • constructive/destructive interference due to sources phase difference
    • ...

    Effect of coherence and incoherence sources

    This PhET simulation (download here, webpage here) shows the importance of coherence in interference phenomenon.

    Young's Double Slit experiment