What is the significance of the curved paths of earthquake waves in the interior of the earth ?

Answer

All the three, P, S and L waves follow curved paths in the interior of the earth which proves that density increases inside the earth.
P and S waves are recorded along the surface upto a distance of 11000 km from the focus of the earthquake. Their velocity also increases with the increase in the depth upto 2900 km. Beyond this S-waves disappear and P-waves travel with reduced velocity.
This process shows that the core of the earth behaves like liquid while mantle upto a depth of 2900 km behaves like solid. On reaching the core, S-waves disappear and P-waves are reflected as a result of which there are no waves for a distance of 5000 km. This area is known as Shadow Zone.
The presence of shadow zone on the surface of the earth shows that earth's crust is composed of heavy materials like nickel and iron whose density is 11-12.