Doppler Effect Moving source stationary observer Doppler Effect
Doppler Effect Moving source, stationary observer:
Doppler Effect Moving source, stationary observer:
Doppler Effect Moving source, stationary observer:
Doppler Effect Moving source, stationary observer:
Doppler Effect Moving source, stationary observer:
Doppler Effect Moving source, stationary observer: Wavelength here Is increased
Doppler Effect Moving source, stationary observer: Wavelength here Is increased Wavelength here Is decreased
Doppler Effect Moving source, stationary observer: This is where the car WAS when the first wave-front was emitted
Doppler Effect Moving source, stationary observer: This is where the car was when the SECOND wave-front was emitted
Doppler Effect Moving source, stationary observer: If the emitted wave has frequency, f then the time between Wave-fronts Is simply the PERIOD, T= 1 f
Doppler Effect Moving source, stationary observer: If the emitted wave has frequency, f then the time between Wave-fronts Is simply the PERIOD, T= 1 f The car has moved a v distance of vs x T, or s f
Doppler Effect Moving source, stationary observer: If the emitted wave has frequency, f then the time between Wave-fronts Is simply the PERIOD, T= 1 f The car has moved a v distance of vs x T, or s f So the wavelength here is INCREASED by vs f
Doppler Effect Moving source, stationary observer: If the emitted wave has frequency, f then the time between Wave-fronts Is simply the PERIOD, T= 1 f The car has moved a v distance of vs x T, or s f So the wavelength here is INCREASED by vs f And the wavelength here is DECREASED by vs f
Source Moving Towards Us: vs • Wavelength decreases by Δλ = f
Source Moving Towards Us: vs • Wavelength decreases by Δλ = f • So λmoving = λstationary – Δλ
Source Moving Towards Us: vs • Wavelength decreases by Δλ = f • So λmoving = λstationary – Δλ v • But since v = f λ, we can substitute for λ (= ) f
Source Moving Towards Us: vs • Wavelength decreases by Δλ = f • So λmoving = λstationary – Δλ v • But since v = f λ, we can substitute for λ (= ) f v fmoving = v - fstationary vs fstationary
Source Moving Towards Us: vs • Wavelength decreases by Δλ = f • So λmoving = λstationary – Δλ v • But since v = f λ, we can subtitute for λ (= ) f v fmoving = v - fstationary vs fstationary ( v f’ = f v - vs )
Doppler Effect and the BIG BANG • How does a star’s motion affect the light? • What does a ‘red shift’ mean? • If hydrogen emits light at a fixed frequency, how can we determine whether a star is moving? • How old is the universe? • How do we know this? • What other evidence is there for the Big Bang model? • How can powerful telescopes tell us what happened billions of years ago?
- Slides: 19
