UNIT OVERVIEW

Have you noticed how an ambulance siren sounds higher-pitched as it approaches, then drops to a lower pitch as it speeds away? This is the Doppler Effect in action. By the end of this unit, you will understand exactly why this happens and be able to calculate the frequency changes involved.

The Doppler Effect is used in many areas of science and technology. It helps doctors monitor blood flow, allows traffic officers to measure vehicle speeds, and provides evidence that our universe is expanding.

What You Will Learn

• How relative motion between a source and observer changes the perceived frequency of waves
• The mathematical relationship that describes the Doppler Effect for sound
• How to apply the Doppler equation to various scenarios involving moving sources and observers
• Real-world applications in medicine, traffic monitoring, and astronomy
• How the Doppler Effect with light reveals that the universe is expanding
• The difference between red shift and blue shift

Real-Life Applications

1. Medical Ultrasound: Doctors use Doppler ultrasound to measure blood flow velocity, detecting blockages and monitoring foetal heartbeats during pregnancy.