You are lying on your side in an Olympic swimming pool with one ear above the surface. A friend of yours, 50 m away in the water, slaps the surface of the water with his hand. The temperature outside is 20°C and the speed of sound in air is 344 m.s¹. The temperature of the water is 15°C and the speed of sound in water is 1480 m-s¹. Calculate: how long it will take to hear the slap with the ear that is above the water;
