Jawabanmu

2014-08-25T22:49:12+07:00
V=300m/s \\ f=400Hz \\ delta\psi= \frac{1}{3}  \\  \\ V=\lambda*f \\ 300=\lambda*400 \\ \lambda=0,75m
 \\ delta\psi= \frac{-deltaX}{\lambda}  \\  \frac{1}{3}= \frac{-deltaX}{0,75}   \\ deltaX=-0,25m=-25cm

tanda minus menunjukkan keterlambatan fase. jadi boleh dihilangkan. Semoga Membantu :D