Two small slits are in a thick wall, $31\mathrm{.}5$ cm apart. A sound source from the behind the wall emits a sound wave toward the wall at a frequency of $2,000$ Hz$.$ Assume the speed of sound is $351$ m$/$s$.$

$($a$)$

Find the $($positive$)$ angle $($in degrees$)$ between the central maximum and next maximum of sound intensity. Measure the angle from the perpendicular bisector of the line between the slits.

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$($b$)$

The sound source is now replaced by a microwave antenna, emitting microwaves with a wavelength of $2\mathrm{.}25$ cm$.$ What would the slit separation $($in cm$)$ have to be in order to give the same angle between central and next maximum of intensity as found in part $($a$)?$

cm

$($c$)$

The microwave antenna is now replaced by a monochromatic light source. If the slit separation were $1\mathrm{.}00$m$,$ what frequency $($in THz$)$ of light would give the same angle between the central and next maximum of light intensity?