A traverse periodic wave described by the expression y=5sin (pi x/3 - 30pi t) (where y and x are in meters and t is in seconds) is established on a string.

Question

By reflecting this wave from a rigid support, standing transverse waves are set up on a stretched string. It is observed that the string is vibrating in its THIRD HARMONIC. What is the length in meters of the string?

Question 5 options:
A)
3

B)
6

C)
9

D)
12

E)
15