If you or any else needs the answer for this it is C. +1.11 m/s.
Answer: two waves with identical crests and troughs meet
Explanation:
My teacher gave me the answer
To solve the problem, it is necessary the concepts related to the definition of area in a sphere, and the proportionality of the counts per second between the two distances.
The area with a certain radius and the number of counts per second is proportional to another with a greater or lesser radius, in other words,
M,m = Counts per second
Our radios are given by
Therefore replacing we have that,
Therefore the number of counts expect at a distance of 20 cm is 19.66cps