Question

how does the doppler effect explain why a sirens pitch increases as it approaches you?
a. the siren moves away from sound waves it has already produced, decreasing their wavelength.
b. the siren moves closer to sound waves it has already produced, decreasing their wavelength.
c. the siren moves closer to sound waves it has already produced, increasing their wavelength.
d. the siren moves away from sound waves it has already produced, increasing their wavelength.

Explanation:

The Doppler effect for sound occurs when the source (siren) moves relative to the observer. As the siren approaches, it moves closer to the sound - waves it has already produced. This causes the wavelength of the sound waves to decrease. Since pitch is inversely related to wavelength (higher frequency means higher pitch), a decrease in wavelength leads to an increase in pitch.

Answer:

B. The siren moves closer to sound waves it has already produced, decreasing their wavelength.