The earth has a radius of 6400km. The inner core of 1000 km radius is solid. Outside it, there is a region from 1000 km to a radius of 3500km which is in molten state. Then again from 3500km to 6400 km, the earth is solid. Only longitudinal (P) waves can travel inside a liquid. Assume that the P wave has a speed of `8kms^(-1)` in solid parts and of `5kms^(-1)` in liquid parts of the earth. Calculate the time after which it will be recorded in a seismometer at a diametrically opposite point on earth if wave travels along diameter.

Explanation

Speed of wave =8 km/s

Speed of wave in liquid =5 km/s
Required time `=[(1000)/(5)+(3500-1000)/(5)+(6400-3500)/(8)]xx2" " [ :. "diameter =radius"xx2]`
`" " =[(1000)/(8)+(2500)/(5)+(2900)/(8)]xx2" " ["time"=("distance")/("speed")]`
As we are considering at diametrically opposite point, hence there is a multiplication of 2.