A tunnelling machine produces vibrations in limestone. The vibrations have a wavelength of 300 m and travel at 4800 m/s.
The vibrations pass into clay, where their speed is 1440 m/s. A row of electronic sensors measures the wavelength in the clay. A person nearby listens for the sound.
Which outcome is expected in the clay?
The person does not hear the sound and the sensors measure a wavelength of 90 m90\ \mathrm{m}90 m.
The person hears the sound and the sensors measure a wavelength of 90 m90\ \mathrm{m}90 m.
The person does not hear the sound and the sensors measure a wavelength of 300 m300\ \mathrm{m}300 m.
The person hears the sound and the sensors measure a wavelength of 1000 m1000\ \mathrm{m}1000 m.