# how does the phase decrease as the wave moves in the direction.delta of phase angle is directly proportional to delta of displacement phase angle=-k x where k is propagation constant and -undicates decrease in phase in the direction of wave.plz explain

SAGAR SINGH - IIT DELHI
879 Points
12 years ago

Dear student,

The phase of a wave refers to a sinusoidal function such as the following:

$x(t) = A\cdot \cos( 2 \pi f t + \theta )\,$
$y(t) = A\cdot \sin( 2 \pi f t + \theta ) = A\cdot \cos( 2 \pi f t + \theta -\pi/2),\,$

where A, f, and $\scriptstyle \theta$ are constant parameters. These functions are periodic with period $\scriptstyle T = 1/f$, and they are identical except for a displacement of $\scriptstyle T/4$ along the $\scriptstyle t$ axis. The term phase can refer to several different things:

• It can refer to a specified reference, such as $\scriptstyle \cos( 2 \pi f t)\,$, in which case we would say the phase of $\scriptstyle x(t)$ is $\scriptstyle \theta$, and the phase of $\scriptstyle y(t)$ is $\scriptstyle \theta -\pi/2$.
• It can refer to $\scriptstyle \theta$, in which case we would say $\scriptstyle x(t)$ and $\scriptstyle y(t)$ have the same phase but are relative to different references.

All the best.

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Sagar Singh

B.Tech, IIT Delhi