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Waves

Wave graphs and intensity

  • 2 things to know
  • Papers 2 and 3

Overview

Recall questions on displacement-distance and displacement-time graphs, representing longitudinal waves graphically, and wave intensity: its equation, units, calculation and dependence on amplitude.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Numbers

Define the intensity of a progressive wave and state its equation in terms of power and area.

Key term

What are the SI units of intensity, how does intensity depend on amplitude, and what happens to the intensity if the amplitude doubles?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    On a displacement–distance graph for a transverse wave, what quantities are plotted on each axis?

    Model answer

    Displacement is on the vertical axis and distance along the wave is on the horizontal axis; the wave profile appears as a sinusoidal curve.

  2. 2

    What does a displacement–time graph for a transverse wave represent?

    Model answer

    It shows displacement on the vertical axis and time on the horizontal axis, representing the oscillation of a single point on the wave.

  3. 3

    How can a longitudinal wave be represented graphically?

    Model answer

    By plotting the displacement of particles (parallel to the wave direction) against position, showing compressions and rarefactions.

  4. 4

    Define intensity of a progressive wave.

    Model answer

    Intensity is the power transmitted per unit area perpendicular to the wave direction.

  5. 5

    State the equation for intensity in terms of power and area.

    Model answer

    Intensity equals power divided by area: I = P/A.

  6. 6

    What are the SI units of intensity?

    Model answer

    Watts per square metre (W m⁻²).

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A wave.
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