1. Sound travels at 1500 m/s in water. How deep is an ocean if the echo from a transmitter takes 4 seconds to reach the receiver? (Hint: remember that four seconds is the time it takes to go to the seabed and back.) 2. A dolphin makes a clicking sound and detects the echo from the fish that is 250 m away. How long was it before it heard the echo?

3. A woman is having an ultrasound scan. The ultrasound travels at 1500 m/s inside the body. The ultrasound transmitter sends out a pulse of ultrasound and it is reflected from the surface 7.5 cm away. How long before the echo is receiving (Remember 7.5 cm is equal to 0.075 m?)