A seismic wave is traveling through the Earth's mantle. The deeper into the mantle the wave goes, the greater the pressure is.

Question

As the pressure in the mantle increases,_________.
the wave's frequency increases.
the wave's speed increases.
the wave's speed decreases.
the wave's frequency decreases.

Answer 1

As the pressure in the mantle increases, the wave's speed increases.

In general, for seismic waves, as they travel through denser materials (which often corresponds to higher pressure and temperature), their speed tends to increase. This is particularly true for both primary (P) waves and secondary (S) waves in the Earth's interior.