Final answer:
You must move to the right side of the road and pull over for emergency vehicles. In an intersection, proceed before pulling over. The Doppler shift in a siren can indicate the ambulance's movement relative to your position.
Step-by-step explanation:
When you encounter an emergency vehicle, such as an ambulance with its siren blaring, you must move to the right side of the road, if possible, to give it the right of way. If you're in an intersection when an emergency vehicle approaches, you should continue through the intersection before pulling over. This is both a matter of safety and legality. Stopping in the middle of an intersection can create hazards for both the emergency vehicle and other traffic.
The Doppler shift is a relevant physical phenomenon here. If you hear the pitch of the ambulance's siren change, it indicates that the vehicle is moving relative to you. A higher pitch means the ambulance is approaching, and a lower pitch means it is moving away. This can help you determine when to pull over and make way for the ambulance.