Parabolic reflectors with microphon located at the focus are used to capture sounds from a distance. The sound waves enter the reflector and are concentrated toward the microphone. How far from the reflector should a microphone be placed if the reflector has a width of 3 feet and a depth of 1.25 feet?

Question

hottchevymanzm · Accepted Answer

The parabola is horizontal so the standard form is:  (  y  −  k      )          2        =  4  p  (  x  −  h  )Since the vertex is at (h, k) and the focus is at (h +p, k), then the microphone must be placed |p feet to the right of the vertex. If the vertex is at (0,0), then h = 0 and k = 0:      y          2        =  4  p  xTo find p, substitute a point. A point on the parabola is (1.25, 1.5) since the depth is 1.25 ft and the width is 3 m (half of it).Hence,  (  1.5      )          2        =  4  p  (  1.25  )2.25=5p0.45=pSo, the microphone should be placed 0.45 ft to the right of the vertex of the reflector.Result:0.45 ft to the right of the vertex of the reflector