Final answer:
When an emergency vehicle with lights and siren is approaching from behind, you should pull over to the right and stop to clear the way. The pitch change of the siren due to the Doppler effect indicates its approach and passage. It is important to yield the right of way for emergency responders to ensure their quick and safe travel.
Step-by-step explanation:
If an emergency vehicle is approaching you from the rear with its lights and siren on, you should pull over to the right and stop. This action is not only a legal requirement in many jurisdictions, but it is also a crucial measure for ensuring that emergency vehicles can reach their destinations as quickly and safely as possible without being impeded by traffic. By moving to the right and stopping, you clear the way for the emergency vehicle and adhere to the rules of the road designed to assist first responders and other emergency services.The sirens and flashing lights of an emergency vehicle, such as an ambulance or fire truck, are indicators that the vehicle is responding to an urgent call. When you hear the Doppler shift of an approaching siren—indicated by a change in pitch as the vehicle gets closer—it alerts you to the need to check your surroundings and prepare to yield the right of way. Once the vehicle has safely passed, you can resume your journey, always following the rules of the road for your safety and the safety of others.
If you are standing on the sidewalk facing the street and an ambulance drives by with its siren blaring, the frequency that you observe will most closely match the actual frequency of the siren when it is in front of you. This is due to the Doppler effect: as the source of the sound approaches, the frequency appears higher; as it moves away, the frequency appears lower. When it is directly in front of you, the relative motion between you and the siren is momentarily perpendicular, so there is no Doppler shift affecting the sound's frequency you hear.