Question 3: the correct answer is True. Did you get it right? Score 1 point.
Question 4 of 10
Dogs can only see in black and white.
Why, in question 3: Sound travels faster in water than in air.
That's true. In water, sound travels at about 1,500 meters per second, more than four times the speed in air, which is about 340 meters per second. In solids, such as steel, it is even faster.
Why does sound travel faster in water?
Sound is a vibration passed from particle to particle. Water is much harder to compress than air, and this makes the vibration spread faster.
Whales take advantage of this: the low-frequency sounds of some species travel hundreds of kilometers through the ocean.
Underwater, however, it is hard to tell where a sound is coming from. The brain calculates direction from the small difference in timing between the two ears, and with sound moving so fast, that difference becomes too short.
Submarines and research ships use sonar: they send out a pulse of sound and measure how long it takes to return, to determine the distance to the bottom or to other objects.
