Red Shift/ Blue Shift The Doppler Effect with Light

# Red Shift/ Blue Shift The Doppler Effect with Light

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## Red Shift/ Blue Shift The Doppler Effect with Light

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1. Red Shift/Blue ShiftThe Doppler Effect with Light

2. Scientists Say: The universe started like this: Here we look at some java applets: 2D big bang 3D big bang Today we’re going to learn why.

3. Increasing λ Increasing f Electromagnetic Spectrum In which direction does the wavelength increase? In which direction does the frequency increase?

4. Stationary Wave Sources L R Q: Does either eye (left or right) observe a different wavelength light? A: No. Both eyes observe the same wavelength, yellow, light. Q: Does either eye (left or right) observe a different wavelength light?

5. Moving Wave Sources L R Q: Does either eye (left or right) observe a different wavelength light? A: Yes. The left eye will see longer wavelength light and the right eye will see shorter wavelength light. Q: Does either eye (left or right) observe a different wavelength light?

6. Q: What happens to the light the right eye see? Q: What happens to the light the left eye sees? Red Shift Blue Shift No Shift Red Shift Blue Shift No Shift Red Shift / Blue Shift, Notes: L R • Wave source approaching (blue shift) • wave fronts are squished together • wavelength is shorter, frequency is higher • so it appears bluer • Wave source moving away (red shift) • wave fronts are spread apart • wavelength is longer, frequency is lower • so it appears redder

7. What Color Does Ashley See? What Color Does Jessica See?

8. A Person Stands on a PlanetThe Planet is Flying Away The person is holding a red and a blue light bulb. A green light bulb grows out of their head.

9. Draw What You’ll See:Label the colors of the light bulbs! green? The person is holding a red and a blue light bulb. A green light bulb grows out of their head. What colors will you see? ?  blue red  ?

10. Green  Yellow Blue  Green Red Infrared* You Would See * Note: Human Eyes Can’t See Infrared

11. The Sun & The Stars • The sun is a star. • The sun and the stars are all made out of hydrogen. • Light from hydrogen leaves a distinctive pattern of black lines (an absorption spectrum).

12. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy This is the absorption spectrum (pattern of black lines) from a close star like our sun.

13. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy If the nearby galaxy wasn’t moving, the absorption spectrum (the pattern of black lines) would be in the same place.

14. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy Is the pattern red shifted or blue shifted?

15. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy The pattern is red shifted since it is shifted towards the red side of the spectrum.

16. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy The pattern is red shifted. — So — Is the nearby galaxy moving towards us or away from us?

17. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy The pattern is red shifted. — So — Is the nearby galaxy moving towards us or away from us?

18. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy The bigger the shift, the faster the light source is moving.

19. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy Which is moving away faster: the nearby galaxy or the faraway galaxy?

20. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy Which is moving away faster: the nearby galaxy or the faraway galaxy?

21. What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy

22. Your Turn The further away a galaxy is, the bigger the ______ shift. So far away galaxies are moving away _______. red blue slower faster

23. Your Turn The further away a galaxy is, the bigger the ______ shift. So far away galaxies are moving away _______. red red blue slower faster

24. Your Turn The further away a galaxy is, the bigger the ______ shift. So far away galaxies are moving away _______. red red blue faster slower faster

25. Scientists’ Conclusions The further away a galaxy is, the bigger the red shift. So far away galaxies are moving away faster. • The galaxies must have been close together in the past. • A tremendous explosion (a big bang) must have made everything explode outward. • That’s why the fastest galaxies are the furthest away.