Check Your Understanding A. Identify what is being asked. Write the answer on the space REMEMBER provided before each number. 1. It is the change in the perceived frequency due to the relative motion of the source and the observer. 2. The perceived frequency when an observer moves toward a source. 3. The perceived frequency when the source moves away from an observer. 4. The perceived frequency when the source moves toward an observer.Unit 13: Mechanical Waves and Sound 5. The perceived frequency when an observer moves away from a source. B. Identify whether each statement is true or false. REMEMBER 1. The Doppler effect occurs when the intensity of the sound changes as a source moves toward or away from a listener. 2. As the source moves toward an observer, the wavelength becomes longer. 3. Doppler effect can only occur if there is relative motion between an observer and a source. 4. Doppler effect can also occur for other types of waves. 5. As an observer moves toward a stationary source, the wavelength of the source will decrease.C. Solve the following problems.. APPLY Items 1-3. A train, moving at a constant speed of 60 m/s, is passing by a stationary observer. The train makes a sound at a frequency of 500 Hz. 1. What will be the frequency perceived by the stationary observer as the train moves towards him? 2. What will be the frequency perceived by the stationary observer as the train moves away from him? 3. What is the total change in frequency heard by the observer as the train moved toward then away