It’s like an oval so round I should say
<h2>Answer: D. Rayleigh wave
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Rayleigh waves are a type of surface acoustic wave that causes particles on the surface of solids to travel along an elliptical path in the vertical plane that contains the direction of wave propagation.
These waves include longitudinal (P wave) and transverse (S wave) movements whose amplitude decreases exponentially as the distance from the surface increases.
This means Rayleigh waves are generated by the interference between the P and S waves on the surface of the Earth.
Often, waterfalls form as streams flow from soft rock to hard rock. This happens both laterally (as a stream flows across the earth) and vertically (as the stream drops in a waterfall). In both cases, the soft rock erodes, leaving a hard ledge over which the stream falls
Set this up as
10 = 40 (1/2)t/28
and solve for t in years.
10/40 = (1/2)t/28
log(0.25) = (t/28) log(0.5)
t = 28 log(0.25) / log(0.5) years = 56 years
Test the answer:
56 years = 2(28 years) = 2 half-lives, so the remaining amount should be 1/2 of 1/2 of the initial amount, i.e. 1/4 of the initial amount, and 10 mg = 1/4 of 40 mg.
