Question

The equation $y=0.02 \sin (500 \pi t) \cos (4.5 x)$ represents

• A. progressive wave of frequency 250 Hz along $x$ -axis
• B. a stationary wave of wavelength 1.4 m
• C. a transverse progressive wave of amplitude 0.02 m
• D. progressive wave of speed of about $350\, m \,s ^{-1}$

Answer 1

Answer: (B)

A stationary wave equation is
$y=A \sin \omega t \cos k x$
Here $k=4.5=\frac{2 \pi}{\lambda}$ or
$\lambda=\frac{2 \pi}{4.5}=1.4$ units.