A singer raises his pitch one octave. What quality of the sound wave has changed?

A.) the speed has increased

B.) the amplitude has increased

C.) the wavelength has increased

D.) the frequency has increased

C). The amplitude has increased

If a singer raises his pitch by one octave this means that he has raised the frequency. So the frequency will be increased.

Frequency is the reciprocal of period which is the duration of time of one cycle in a repeating event.

Frequency and pitch are directly proportional. So the greater the pitch of the singer the greater its frequency gets increased.

This means the wavelength has also decreased as it is inversely proportional to the frequency.