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Add overlapping displacements

When waves overlap, the resultant displacement at a point is the algebraic sum of the individual displacements: $y_{\mathrm{resultant}}=y_1+y_2$ . The waves then continue propagating after the overlap.

Keep the signs

Displacements on the same side of equilibrium add; opposite displacements partially or completely cancel. Equal opposite pulses can produce zero displacement at an instant without destroying either wave.

Connect to interference

Repeated superposition of coherent waves can create stable maxima and minima. A diffraction pattern extending beyond a geometrical shadow is evidence that wave overlap and interference are involved.

Common trap

Do not add amplitudes as positive magnitudes only, and do not treat destructive interference as permanent disappearance of the waves.

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Early theories of light suggest that a geometrical shadow of the slit will be observed on the screen. Explain how the diffraction pattern formed on the screen provides evidence for the wave theory of light.

C.3 Wave phenomena is secure when you can connect the physical picture to the equation and its limits.

Wavefronts and rays
Reflection, refraction and Snell’s law
Refractive index and total internal reflection
Superposition, coherent sources and interference
Young’s double-slit pattern

C.3.5—Superposition

Apply Superposition

Retrieve the Core C.3 Wave Phenomena Model

C.3.5 Exam Analysis