Question text1. The figure below shows a simple model of a planet with two concentric layers. The planet’s core radius is [math: r=600km] and the whole planet’s radius is [math: R=6000km] (Figure not drawn to scale !). Layer 1 (mantle) is solid and has a uniform P wave velocity [math: VP1=8km/s] and uniform S wave velocity [math: VS1=4km/s]. The second layer (the core) is liquid and has a uniform P wave velocity [math: VP2=5km/s] and a uniform S wave velocity [math: VS2=0km/s]. The figure also shows half of the S wave shadow zone between points B and C, subtended by the angle [math: a]. In this region there are no S waves detected from an earthquake that occurs at point A. a) Calculate the angle [math: a] to two significant figures in degrees, thus finding the half angle of the S wave shadow zone. [math: a=] Answer 1 Question 1[input] degrees [4]b) If an artificial earthquake is generated at point A (at the surface), calculate the time it takes for an S wave to arrive at point B and the time it takes for a P wave to travel to point C. Give your answers in minutes to two significant figures. Hint: Look at the triangle AOBTime for S wave=Answer 2 Question 1[input] minutes [3]Time for P wave=Answer 3 Question 1[input] minutes [3]多项填空题