A taut string (2 m) is fixed at both ends and plucked. The speed of waves on this string is 3 x 104 m/s. (See figure.)
A finger is placed at point B (see figure; B is midway between the ends), and the string is lightly plucked, so that a waveform exists on the whole string. (Thus a node exists at B.) What is the lowest frequency that may be heard in this case?