Final answer:
The Doppler effect causes a change in frequency of a wave as the source moves relative to the observer. The question asks for the speed of the ambulance when the observed frequency is different from the emitted frequency. The temperature reading on the observer's thermometer is not affected by the Doppler effect.
Step-by-step explanation:
The question is asking about the effect of the Doppler shift on the observed frequency of a sound source.
The Doppler effect is the change in frequency of a wave as the source moves relative to the observer.
In this case, the siren on the moving ambulance emits a sound at 1200 Hz, but the stationary observer perceives a frequency of 1130 Hz.
To calculate the speed of the ambulance, we can use the formula:
v = fo - fs / fs * v_sound
where v is the velocity of the observer, fo is the observed frequency, fs is the emitted frequency, and v_sound is the speed of sound. Plugging in the given values, we have:
20 m/s = 1130 Hz - 1200 Hz / 1200 Hz * v_sound
Simplifying the equation, we find that the speed of sound is approximately 343 m/s.
To convert the speed of the ambulance to mph, we can use the conversion factor 1 m/s = 2.237 mph.
Therefore, the speed of the ambulance is approximately 44.74 mph.
So, the temperature reading on the observer's thermometer would not be affected by the Doppler effect.