For water waves, sound, light and microwaves, describe a two-source arrangement, how coherence is achieved, what is measured/observed, and a useful controlled variable. Describe a one-source comparison. For in-phase sound sources, λ=0.80 m and the paths to a microphone are 2.0 m and 2.4 m. Predict the observation and state an additional condition for near-total cancellation.

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Shared vibration/signal or one wave split into two provides coherence. Observe water amplitude lines, microphone signal variation, optical fringes and microwave receiver variation. Blocking one source removes two-source fringes. Path difference0.40m=λ/2 gives a minimum; near-equal amplitudes are needed for cancellation. Give water apparatus/coherence/observation and fixed depth or frequency. Give shared-generator speakers, microphone scan and fixed geometry. Give single-source double slit, screen/fringe measurement and fixed D/a. Give microwave two slots, receiver scan and fixed polarisation/frequency. Explain the one-source comparison. Use 2.4−2.0=0.40=λ/2 to predict destructive interference. State approximately equal arriving amplitudes for a near-zero minimum.

Explain four interference experiments

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