The wavelength of a wave is obtained by taking the ratio of wave speed and frequency.
The wavelength of the heated wave is 9.8 m. Hence, option (b) is correct.
What is frequency of a wave?
The number of oscillations completed by a wave in one second is known as the frequency of a wave. It is expressed as the ratio of the velocity of the wave to its wavelength.
Given data-
The wavelength of the wave is,
.
The velocity of the wave is, v = 9.8 m/s.
The mathematical expression for the frequency of the wave is,

Solving as,

Now, with constant frequency and the double magnitude of velocity (v' = 2 × 9.8 = 19.6 m/s). The wavelength of the heated wave is calculated as,

here,
is the wavelength of the heated wave.
Solving as,

Thus, we can conclude that the wavelength of the heated wave is 9.8 m. Hence, option (b) is correct.
Learn more about the frequency of wave here:
brainly.com/question/1324797