Today as i was driving i had to stop because a cop car was coming my way and needed to pass me. As a driver, it is just a procedure to pull over to the side of the road and wait for the cop to pass, then proceed on my way to wherever i was going without thinking twice about the cop car that had just passed. However, today i was listening extra carefully and thought to myself, "Why does the sound increase as it is coming towards me, but as soon as it passes, it decreases?"
Thinking back to previous physics units this year, i remembered the Doppler Effect. The doppler effect is the shift in frequency and wavelength of waves which results from a source moving with respect to the medium. As the cop car was coming towards me, it had a small wavelength but high frequency and as it went away from me, it had longer wavelengths and lower frequency. Even though the siren stayed at the same pitch and loudness at all times from the cop car, to the outsiders, like me, the sound increased and then decreased as it passed me and kept going further.
The Doppler Effect is not just found in cop cars but almost anywhere!! Water waves, sound waves, light waves and etc, the doppler can be proven many ways. For example, when you are on a boat, the waves in front of the boat are so compact and close together that the trail behind the boat are long waves that the travelers can see a pathway of waves. The Doppler Effect is a neat way to see how where a person can be, there are many different oucomes of how sound, light, or water can be portrayed. Physics is EVERYWHERE!!
For more information on the doppler effect, check out this cool video!