Red and Blue Shift

1. Red and Blue Shift

2. The Doppler Effect

3. Sound waves travel out from the bike at the same speed in all directions

4. Sound waves still travel out from the bike at the same speed in all directions but the bike is moving and the waves are squeezed together in the direction of travel and less tightly packed in the opposite direction Sound waves which are closer together are higher in PITCH than those which are further apart.

6. The light is always redder than it should be from distant galaxies.

7. Red and Blue shift Red and blue shift does not measure the velocity of a galaxy or star relative to us but only a component of that velocity called the radial velocity Radial velocity Actual velocity

8. Red and Blue Shift   s Increasing wavelength

9.   s Increasing wavelength   s Increasing wavelength Red And Blue Shift  is positive for red shift  s is negative for blue shift Use –Δλ in calculations So by inspection you can see whether the object is approaching or receding

10. Red and Blue Shift f An increase in wavelength is a decrease in frequency Use positive Δf for consistency  f = f s - f f fs Increasing wavelength Increasing frequency

11. Calculating Velocities

12. Calculating Radial Velocities

13. Calculation The wavelength of the hydrogen  line in the laboratory is 656.285 nm. The same line is observed to occur at 656.255 in the star Vega.. Is it approaching or receding? Calculate its radial velocity (taking c = 3 x 108m) This object is approaching

14. Calculation c = 3 108ms-1

15. Stellar Data

16. ECLIPSING BINARIES AND REDSHIFT

18. LightIntensity time

23. time Velocity of recession +200 0 -200