Keep trying until you find the correct answer.

1. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

2. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

3. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

4. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

5. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

6. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

7. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

8. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

9. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
   

   1.   ?    0
   2.   ?    ¹/₂π (90°)
   3.   ?    π (180°)
   4.   ?    ³/₂π (270°)

10. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

11. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

12. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

13. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

14. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

15. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

16. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

17. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

18. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

19. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

20. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

21. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

22. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

23. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

24. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

25. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

26. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

27. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

28. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

29. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

30. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

31. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

32. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

33. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

34. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

35. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

36. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

37. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

38. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

39. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

40. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

41. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

42. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

43. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

44. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

45. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

46. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

47. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

48. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

49. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

50. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

51. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

52. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

53. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

54. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

55. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

56. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

57. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

58. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

59. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

60. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

61. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

62. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

63. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

64. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

65. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

66. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

67. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

68. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

69. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

70. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

71. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

72. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

73. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

74. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

75. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

76. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

77. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

78. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

79. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)

80. Consider the two loudspeakers in the diagram below. The loudspeakers, shown at t = 0, are playing sound of the same frequency. What is the total phase difference, Δφ = (φ_bottom 0 − φ_top 0) + 2π ^Δx/_λ, by which the bottom blue wave leads the top red wave?
    

    1.   ?    0
    2.   ?    ¹/₂π (90°)
    3.   ?    π (180°)
    4.   ?    ³/₂π (270°)