Doppler Effect

1. What?

1.1. Change in frequency of a wave for an observer moving relative to the source of the wave

2. Why?

2.1. Moving source

2.1.1. Change of wavelength

2.2. Moving observer

2.2.1. Change of wave speed

3. Who?

3.1. Doppler Effect was proposed by an Austrian physicist Christian Doppler

4. 2. Moving Source

5. Principle

5.1. 1. Moving source approaching a stationary observer, the receive pitch will then become higher and vice versa

5.2. 2. A moving observer approaching a stationary source, the reveived pitch will then become higher and vice versa

5.3. 3. When both of the source and observer moving towards with each others, the received pitch will then become higher and vice versa

6. Formula

6.1. 1. Original wave equation: v = fλ

6.2. 3. Moving Observer

6.3. 4. General Form

7. Concept

7.1. Source moving towards observer

7.1.1. Sound wave has higher frequency

7.2. Source moving away from observer

7.2.1. Sound wave has lower frequency

8. Examples

8.1. When an ambulance is approaching, the whistle has a higher pitch than normal

8.2. Determine the speed of car by using radar gun

8.3. Gauge the line-of-sight velocities for stars