The Earth's mantle is denser near the core than it is near the crust, so the speed of seismic waves varies throughout the interior. Therefore, seismic waves are refracted as they travel deep within the Earth. This refraction is used to help model the density of interior layers. A seismic longitudinal P wave travelling at 8.5 km/s encounters a region in which the propagation speed is 12.5 km/s.
If the P wave strikes the boundary between regions at an angle of 65 degrees with respect to the boundary, what is the angle of refraction θ in the dense region?
