A pair of speakers separated by distance d = 0.900 m are driven by the same oscillator at a frequency of 670 Hz. An observer originally positioned at one of the speakers begins to walk along a line perpendicular to the line joining the speakers as in the figure below.
(a) How far must the observer walk before reaching a relative maximum in intensity?
Here I calculated the wavelength 343/670= 0.511940
Then I did (0.9)^2 - (0.5119)^2/(2*0.5119) and got 0.535m as my answer, which is correct.
(b) How far will the observer be from the speaker when the first relative minimum is detected in the intensity?
I can't seem to find the right answer for part b.
I did [(0.9)^2-((0.5119)^2/4)]/0.5119
to get 1.45
but that is not the correct answer. Can someone tell me what I did wrong? thank you!