Two speakers are placed along the x$-$axis $1\mathrm{.}50$ m apart and emit sound waves in phase. A

microphone placed on the x$-$axis in front of both speakers measures the sound from the

speakers. Both speakers emit sound waves at the same frequency and amplitude. The output

frequency is initially set to $300$ Hz$.$

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$($a$)(6$ points$)$ At this frequency, does the microphone detect maximum intensity or minimum

intensity?

$($b$)(6$ points$)$ The frequency of the sound is steadily increased from $300$ Hz to $1100$ Hz$.$ As the

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frequency is increased, how many times does the microphone detect zero sound intensity?

$($c$)(6$ points$)$ As the frequency is increased from $300$ Hz to $1100$ Hz$,$ how many times does the

microphone detect maximum sound intensity?