Find the frequency of a sinusoidal wave whose time period is 40 milliseconds.

Correct option is B

​$$f = \frac{1}{T}$$

$$\text{where:} \bullet \ f \text{ is the frequency in Hertz (Hz).} \\\bullet \ T \text{ is the time period in seconds.}$$​​​

​$$\textbf{Given:} \bullet \ \text{Time period, } T = 40 \text{ milliseconds} = 40 \times 10^{-3} \text{ seconds} = 0.04 \text{ seconds}$$

$$\textbf{Calculation:}$$

$$f = \frac{1}{0.04} = 25 \text{ Hz}$$​​​​