Question

a periodic wave travels outward from a source. the waves frequency can be changed. the speed that the wave moves forward does not change. complete the statement. if the frequency of the wave is decreased, its wavelength will.

Explanation:

Step1: Recall wave - speed formula

The wave - speed formula is $v = f\lambda$, where $v$ is the wave speed, $f$ is the frequency, and $\lambda$ is the wavelength.

Step2: Rearrange the formula for wavelength

We can rewrite the formula as $\lambda=\frac{v}{f}$.

Step3: Analyze the effect of frequency change

Since $v$ is constant and $f$ is decreased, when $f$ in the denominator of $\lambda=\frac{v}{f}$ gets smaller, the value of $\lambda$ (wavelength) will increase.

Answer:

increase