MCAT TBR Physics Section 5, Passage 6-Question 40

[4563728]

The passage says, "Studies show that 2 waves of differing wavelengths and amplitudes could pass through each other without any distortion in their wavelength or amplitude."

Question 40 then asks, "How can it be explained that when two deep-water ocean waves pass through the same point simultaneously, the water level neither rises or drops?"

A. The wavelengths do not change when two waves pass through one another.
B. The wavelengths do change with 2 waves pass through one another
C. Two passing waves must have gone undergone perfectly constructive interference at that point.
D. Two passing waves must have gone undergone perfectly destructive interference at that point.

I picked option A, that basically repeats the statement in the passage, "studies show that two waves of differing wavelengths could pass through each other without any distortion in the wavelength or amplitude," but that wasn't the correct answer. Instead it says the two waves had undergone perfect destructive interference. But doesn't this answer completely negate what is said in the passage? The explanation only confused me more and I would really appreciate any help on the problem. Thanks!

---

Members don't see this ad.

 

[BerkReviewTeach]

The passage says, "Studies show that 2 waves of differing wavelengths and amplitudes could pass through each other without any distortion in their wavelength or amplitude."

Question 40 then asks, "How can it be explained that when two deep-water ocean waves pass through the same point simultaneously, the water level neither rises or drops?"

A. The wavelengths do not change when two waves pass through one another.
B. The wavelengths do change with 2 waves pass through one another
C. Two passing waves must have gone undergone perfectly constructive interference at that point.
D. Two passing waves must have gone undergone perfectly destructive interference at that point.

I picked option A, that basically repeats the statement in the passage, "studies show that two waves of differing wavelengths could pass through each other without any distortion in the wavelength or amplitude," but that wasn't the correct answer. Instead it says the two waves had undergone perfect destructive interference. But doesn't this answer completely negate what is said in the passage? The explanation only confused me more and I would really appreciate any help on the problem. Thanks!

The statement you are quoting from the passage in general, and applies if the two waves have different wavelength (frequencies), In essence, they are generating a beat frequency (beat wave), and the beat wave has points of zero displacement where the two waves intersect at points of zero displacement for each of the individual waves.

The question, on the other hand, deals with two waves of identical wavelength. The question also emphasizes that the point of no displacement is set and not a random occurrence (like the general statement from the passage), which can only be explained by destructive interference.