5. Two speakers are spaced 15 m apart and are both producing and identical sound wave. You are standing at a spot as pictured. What would be the frequency produced by the speakers create perfectly constructive interference? Assume n=1 and v=343 m/s
A. 213.04 Hz
B.256.70Hz
C.186.68Hz
D.233.14Hz
6.one brand of dog whistle claims a frequency of 25 kHz for its product. What is the wavelength of this sound (the speed of sound in air is 343m/s)
A.0.01372 m
B.0.02181 m
C.0.01748 m
D. 0.011654 m
7.When astronomers observe the spectra of distant galaxies, they notice that the hydrogen emission lines are shifted noticeably toward the red end of the visual spectrum, a phenomenon called red shift. Red is the lowest frequency of visible light. What does red shift indicate about the movement of distant galaxies?
A. The galaxies are moving toward us.
B. the galaxies are moving away from us
C. The galaxies are the same distance away from us as they always have been.
D. We cannot tell anything from this information.