Four Waves Are Described by the Following Expressions, Where Distances

question 52

Multiple Choice

Four waves are described by the following expressions, where distances are measured in meters and times in seconds. I y = 0.12 cos(3x - 21t)
II y = 0.15 sin(6x + 42t)
III y = 0.13 cos(6x + 21t)
IV y = -0.23 sin(3x - 42t)
Which of these waves travel in the +x direction?

• A) I and II
• B) I and III
• C) II and IV
• D) I and IV
• E) II and III

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