Answer:
The air-water interface is an example of<em> </em>boundary. The <u><em>transmitted</em></u><em> </em> portion of the initial wave energy is way smaller than the <u><em>reflected</em></u><em> </em> portion. This makes the <u><em>boundary</em></u> wave hard to hear.
When both the source of the sound and your ears are located underwater, the sound is louder because the sound waves can <u><em>travel directly to your ear</em></u>.
Explanation:
The air-to-water sound wave transmission is inhibited because more of reflection than transmission of the wave occurs at the boundary. In the end, only about 30% of the sound wave eventually reaches underwater. For sound generated underwater, all the wave energy is transmitted directly to the observer. Sound wave travel faster in water than in air because, the molecules of water are more densely packed together, and hence can easily transmit their vibration to their neighboring molecules, when compared to air.
R = radius of the loop
m = mass of the roller coaster car
for looping the loop critical speed at the top is given as
v₀ = critical speed at the top = sqrt(2gR)
given that :
v = speed of crossing at the top = 2 v₀ = 2 sqrt(2gR)
F = normal force at the top in downward direction
W = weight in downward direction = mg
force equation at the top is given as
F + W = m v²/R
F + mg = m (2 sqrt(2gR))²/R
F + mg = m (4 x 2 gR)/R
F + mg = m (8gR)/R
F + mg = 8 mg
F = 7 mg
F/(mg) = 7
so the ratio comes out to be 7:1
I think the correct answer would be one half the wavelength. Waves would "feel bottom" when the water is at the depth of 0.5 of the wavelength. "Feel bottom" is a term used to describe that the depth of water affects the wave properties. Hope this answers the question.
vibrations in strings, ripples on water surface and electromagnetic waves.