14. You are standing at a rail crossing on a sunny 35C day waiting for a high-speed train to pass. As it is approaching you it begins to sound its horn which has a frequency of 622 Hz. If the train is travelling at 170 km/h, calculate the frequency you would hear when... a. It is approaching you. (4) b. after it has passed you. (3) 15. A standing wave is a special type of superposition that occurs. Briefly describe what happens and show a labelled diagram. (nodes and anti-nodes) (5 ) of 4