Doppler Effect
Key Points
1. Redshift/blueshift tells us direction 2. The amount of the shift tells us speed 3. Distance doesn't play a role
A bright star is moving toward Earth. If you were to look at the spectrum of that star, what would it look like? A. an absorption spectrum that is redshifted relative to a stationary star B. an emission spectrum that is redshifted relative to a stationary star C. a continuous spectrum that is blueshifted relative to a stationary star D. an absorption spectrum that is blueshifted relative to a stationary star E. a continuous spectrum that is redshifted relative to a stationary star
Answer:
Stars that are moving away from you have spectral lines that are ____ shifted while stars moving toward you have spectra that are ____ shifted. If a star is moving ____ the spectral lines will be shifted a lot while a star that is moving ____ will show very little shift in its spectrum.
Answer:
When a source is moving away from you, the doppler effect causes the light to: A. shift toward longer wavelengths B. become bluer C. change in velocity D. both A and C E. both B and C
Answer:
You are in a spaceship flying toward two stationary stars. Star A is really far away and Star B is nearby. Which star will have the largest blueshift? A) Star A B) Star B C) they will have the same blueshift D) cannot tell from the information given
Answer:
You observe the two redshifted spectra shown below. Which of the following statements best describes the motions of the two sources? A. Source A is moving faster than B. B. Source B is moving faster than A. C. Both are moving with the same speed. D. Cannot tell from these spectra
Answer:
Doppler Effect
The change in wavelength of sound or electromagnetic radiation due to the relative motion along the line-of-sight between the observer and the source.
Redshifted
When source and observer are moving away from each other, waves get stretched out, which means the wavelength gets longer and the light becomes redder
Blueshifted
When source and observer are moving toward each other, waves get compressed, which means the wavelength gets shorter and the light becomes bluer
