the echo time t = 10 s
speed of the water wave v = √K/ρ ................
(1)
bulkmodulus of the water K = 2*109
N/m2
density of sea water ρ = 1.025*10
3 kg/m
3
the velocity v = 2d/t ...................
(2)
compare eq (1) and (2) , we get
2d/t = √K/ρ
dept of the ocean is
d
= (t / 2)√K/ρ
= (10 s/2)√[(2*109
N/m2)/(1.025*103 kg/m3)]
= 6.98*103 m
= 6.98 km
= 7 km (approximately)