1. Doppler Effect and Red/blue Shift

2. Doppler Effect

3. Doppler Effect
Doppler effect is the apparent change in frequency of a wave caused by the relative movement of the source to the observer.

4. Doppler Effect

5. Doppler Effect

6. Doppler Effect
In dry air at 20° C sound travels at m/s.

7. Doppler Effect
… but what happens when the object emitting the sound is moving?

8. Doppler Effect

9. Doppler Effect
Remember reference frames and relative velocity. A truck is traveling forward 10 m/s and a man inside the truck bed throws the ball 5 m/s forwards. What is the relative velocity of the ball for an observer on the ground?

10. Doppler Effect
A truck is traveling forward 10 m/s and a man inside the truck bed throws the ball 5 m/s backwards. What is the relative velocity of the ball for an observer on the ground?

11. Doppler Effect
From the reference frame of the fire truck one of the frequencies emitted by the siren is 1000 Hz. The fire truck is also moving at 30 m/s. What is the frequency of the sound wave when the fire truck is moving toward an observer? Remember 𝑓=𝑣/λ.

12. Doppler Effect
From the reference frame of the fire truck one of the frequencies emitted by the siren is 1000 Hz. The fire truck is also moving at 30 m/s. What is the frequency of the sound wave when the fire truck is moving away from an observer? Remember 𝑓=𝑣/λ.

13. Doppler Effect
An Indy race car engine emits a frequency at 800 Hz and propels the car to a velocity of 80 m/s. What would be the frequency of the sound wave when the car is moving toward you? Remember 𝑓=𝑣/λ.

14. Doppler Effect
An Indy race car engine emits a frequency at 800 Hz and propels the car to a velocity of 80 m/s. What would be the frequency of the sound wave when the car is moving away from you? Remember 𝑓 =𝑣/λ.

15. Redshift and Blueshift
Redshift occurs whenever a light source moves away from an observer causing the electromagnetic light to appear to have a lower frequency and longer wavelength.

16. Redshift and Blueshift
Blueshift occurs whenever a light source moves toward an observer causing the electromagnetic light to appear to have a higher frequency and shorter wavelength.

17. Redshift and Blueshift
Diffraction - is the slight bending of light as it passes around the edge of an object. The amount of bending depends on the relative size of the wavelength of light to the size of the opening.

18. Redshift and Blueshift
Spectrum of Atoms

19. Redshift and Blue
Fraunhofer lines

20. Redshift and Blueshift

21. Redshift and Blueshift

22. Redshift and Blueshift
Most objects in space have a redshift, which is evidence of an expanding universe and the big bang. If an object is moving away from Earth with a velocity of 1.5x10⁷ m/s, what color and frequency would orange light with a wavelength of 650 nm appear to us on Earth?

23. Redshift and blueshift
In the local group of galaxies the Milky Way and Andromeda galaxies are on a collision course, which is causing a blue shift.

24. Redshift and Blueshift
The distance between the two galaxies is 2.08x10²² m and it will take 2.5x1017 s before it collides. Find the relative velocity of the Andromeda galaxy.
Find the frequency green light at with a wavelength of 550 nm would appear to us on Earth?