Answer :
The frequency is (40) / (20 seconds) = 2 per second = 2 Hz.
The period is 1/(frequency) = 1 / (2 per second) = 1/2 second .
Answer : Time period will be 0.5 seconds.
Explanation : We can use the formula as;
f = c / λ
f = wave speed c (units m/s) / wavelength λ (units m).
Here, c = 40 and λ = 20;
f = 40 / 20 = 2 Hz
The formula for finding time period is:
[tex] T (period) = \frac{1}{f} [/tex] where f = frequency
We have, f = 2 Hz;
[tex] T (period)= \frac{1}{2} [/tex] = 0.5 second.
Therefore, time period will be 0.5 seconds.