The students observe that the pitches of the sounds from the fire truck and the
ambulance siren are different. The siren for each vehicle has a different pitch, as shown
in Figure 2. The ambulance siren has sound waves with a higher pitch than sound
waves from the fire truck siren.
Figure 2. Pitches of Emergency Sirens
m
high-pitched sound
o
ambulance
low-pitched sound
fire truck
Which evidence from Figure 2 best supports the answer to Part A?
The ambulance sound waves have fewer waves and a longer wavelength.
The fire truck sound waves have fewer waves and a shorter wavelength.
The ambulance sound waves have more waves and a shorter wavelength.
The fire truck sound waves have more waves and a longer wavelength.

So, option 3 or the ambulance sound waves have more waves and shorter wavelength is the correct reason for ambulance siren having higher pitch compared to fire truck siren

Explanation:

Pitch of any sound wave is determined as the clarity in frequency of notes or the number of times a cycle is repeated for a single second. So pitch is similar to frequency. And frequency is the measure of number of complete cycles in a second. So if the ambulance siren has higher pitch compared to siren of fire truck. Then this means the frequency of ambulance siren is greater than the fire truck siren. As the frequency is more, then from the given options, choice 3 is correct. The ambulance siren have more waves and shorter wavelength. As more the frequency or number of waves, lesser or shorter is the wavelength of sound wave from ambulance.