Final answer:
The question pertains to the Doppler effect in Physics, where the observed frequency of a sound shifts as the source moves relative to an observer, such as with a vehicle approaching or leaving a parking space.
Step-by-step explanation:
The question seems to relate to the physics concept of the Doppler effect, which is when the frequency of a sound wave changes for an observer moving relative to its source. When a vehicle is going into or out of a parking space, the frequency of the sound its engine or horn makes may appear higher as it approaches and lower as it recedes, in comparison to the stationary frequency. This is due to the Doppler shift, which is the change in frequency and wavelength of a wave from a moving source with respect to an observer.
The answer to the GRASP CHECK would therefore be: a. when it is coming toward you, because as the ambulance approaches, the sound waves are compressed leading to a higher frequency than when it moves away from you. This is applied in everyday life, such as when driving to gauge the approach of emergency vehicles or crossing the street to ensure the safety of pedestrian movement.
Understanding the Doppler effect can help predict and react to real-world situations involving waves, including sound and light. For instance, knowing how far a car is and its speed, one can determine if it is safe to cross the road based on the perceived frequency changes of its engine sound.