Answer: Option (b) is the correct answer.
Explanation:
The time taken by a wave crest to travel a distance equal to the length of wave is known as wave period.
The relation between wave period and frequency is as follows.
[tex]T = \frac{1}{f}[/tex]
where, T = time period
f = frequency
It is given that wave period is 18 seconds. Therefore, calculate the wave period as follows.
[tex]T = \frac{1}{f}[/tex]
or, [tex]f = \frac{1}{T}[/tex]
= [tex]\frac{1}{18 sec}[/tex]
= 0.055 per second (1 cycle per second = 1 Hertz)
or, f = [tex]5.5 \times 10^{-2} hertz[/tex]
Thus, we can conclude that the frequency of the wave is [tex]5.5 \times 10^{-2} hertz[/tex].
