The figure shows two waves traveling in the positive-x direction. The phase difference between these two waves is closest to
A) 1.0 radians.
B) 1.5 radians.
C) 2.0 radians.
D) 2.5 radians.
E) 3.0 radians.

Question

The figure shows two waves traveling in the positive-x direction. The phase difference between these two waves is closest to
A) 1.0 radians. 
B) 1.5 radians. 
C) 2.0 radians. 
D) 2.5 radians. 
E) 3.0 radians.

Quizplus · Accepted Answer

From the figure, we can see that the two waves have peaks and troughs that are not aligned. The phase difference is the amount by which one wave is shifted relative to the other. We can see that the first peak of the blue wave is aligned with the second trough of the red wave. This represents a phase difference of half a wavelength or pi radians (since the two waves have the same wavelength). Similarly, we can see that the second peak of the blue wave is aligned with the first trough of the red wave. This represents a phase difference of one wavelength, or 2 pi radians. However, since the second peak of the blue wave is closer to being aligned with the second trough of the red wave (instead of the first trough), the phase difference is closer to 1.5 radians. Therefore, the closest choice is B) 1.5 radians.

The Figure Shows Two Waves Traveling in the Positive-X Direction