A high-frequency acoustic pulse is transmitted downwards from the surface of the ice shelf. The pulse reflects off the boundary between the bottom of the ice shelf and the ocean water, and returns to the surface detector.

• The total time taken for the pulse to travel down to the bottom of the ice shelf and back to the detector is $0.18s$.
• The speed of the acoustic pulse in the ice is $3800m/s$.

Calculate the thickness of the ice shelf (the distance from the surface detector to the bottom of the ice).

Use the equation:

$$distance\; travelled=speed\times time$$

The seismic transducer emits an acoustic wave with a frequency of $2500Hz$.

• The speed of the acoustic pulse in the ice is $3800m/s$.

Calculate the wavelength of this acoustic wave in the ice.

Use the equation:

$$wave\; speed=frequency\times wavelength$$

As the acoustic wave travels from the solid ice shelf into the liquid ocean water below, its speed decreases.

Complete the following sentences to describe what happens to the properties of the acoustic wave as it enters the ocean water. Choose your words from: decreases, increases, or stays the same.

• The frequency of the acoustic wave _______________
• The wavelength of the acoustic wave _______________