The Doppler Effect
The other night I was sitting at my kitchen counter when I heard the wailing of sirens coming from off in the distance. The frequency and amplitude of the sirens was quiet at first because the emergency vehicles were so far away. However, the sound grew increasingly louder and louder and within the next minute, an ambulance sped past my house. As the sound of the ambulance died out, I heard more sirens coming. Just like the ambulance, the frequency and amplitude of the siren was quiet at first, but as the fire truck came closer and closer to my house the sound was growing louder and louder. The sound of the sirens hit their peak when they were passing by directly in front of my house. However, the frequency and amplitude was only at its peak for a moment for the vehicles kept moving and the sound was receding, its frequency and amplitude getting quieter and quieter once again. This process is called the Doppler Effect! I couldn't believe it! I had coincidentally learned about the Doppler Effect that night and I now understood what Mr. Fullerton meant when he would say "Doppler Effect" every time we heard sirens outside the classroom window.