Choose the correct answer:
1. The echo-receiver of a sonar attached to a ship receives the echo from the bottom of the sea 3 seconds after the ultrasonic waves were sent into the sea.
If the speed of sound in water is 1400 \(m/s\), what is the depth of the sea? \(m)
If the speed of sound in water is 1400 \(m/s\), what is the depth of the sea? \(m)
2. Pitch of a sound is determined by its__________.