SAT Subject Physics Practice Question 254: Answer and Explanation

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Question: 254

25. Two traveling waves of equal frequency, one of amplitude 4 cm and the other of amplitude 6 cm, superimpose in a single medium. Which of the following best describes the amplitude, A, of the resultant wave?

A. 2 cm ≤ A ≤ 10 cm
B. A = 5 cm
C. A = 10 cm
D. 10 cm ≤ A ≤ 12 cm
E. 12 cm ≤ A ≤ 24 cm

Correct Answer: A

Explanation:

If these waves interfere completely destructively, the amplitude of the resultant wave will be 6 cm – 4 cm = 2 cm. If they interfere completely constructively, then the amplitude of the resultant wave will be 6 cm + 4 cm = 10 cm. In general, then, the amplitude of the resultant wave will be no less than 2 cm and no greater than 10 cm.

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