Answer:
Option C
Explanation:
According to question , the progressive wave is represents by y=12 sin (5t-4x) cm
Comparing this equatiuon with standard equation of progressive wave,
$y= A \sin(\omega t-kx)$
So, we have A=12
$\omega$ = 5
$\Rightarrow$ k=4
Here, ($\omega $ t- kx) is phase difference = $\frac {\pi}{2}$
$\therefore$ 5t-4x = $\frac{\pi}{2}$
When t=0, 4x= $\frac{\pi}{2}$
$\therefore$ x= $\frac{\pi}{8}$ cm
