Coastal monitoring stations record sound produced by ocean waves.
One signal has a frequency of 4.2 Hz.
The speed of sound in air is 336 m/s.
State the type of sound represented by this signal.
Calculate the wavelength for this signal as it travels through the air.
A monitoring station is 42 km from the region of ocean producing the sound.
Calculate how long the sound takes to reach the monitoring station.
The sound crosses into another gas in which its speed is lower than in air.
State the change in wavelength as the sound crosses this boundary.