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wave question

A microwave transmitter directs wave towards a metal plate. The detector is placed at a position where the intensity is a minimum. When it is moved a distance of 144mm it passes through nine maxima and reaches the ninth minimum from the starting point: Calculate the wavelength of the microwave. I throught it was gonna be 9λ=144mm But somebody told me 9λ/2=144mm " nine maxima and reaches the ninth minimum" puzzle confuses me. oh yes and when its saying minimum point in the question does it mean I have to start where the node is since it is stationary wave or where the maximum negative amplitude is?
One wavelength of a standing wave contains two maxima.

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So nine maxima correspond to 9/2 wavelengths.
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Yes a minimum is a node. Zero amplitude.

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