One of the absorption lines of hydrogen has a rest wavelength of ...

[rosent76]

One of the absorption lines of hydrogen has a rest wavelength of 656 nm (at rest means with respect to the observer, like in a lab). You observe several stars and measure the wavelength of this same hydrogen absorption line in each star.
 
  Based on the measured wavelength of this line, which star is moving towards the Earth the fastest?
  A) 670 nm B) 640 nm C) 656 nm D) 630 nm E) 680 nm

Question 2

Which of the following telescopes is best suited for studying the hottest intergalactic gas (10 million K) in a cluster of galaxies?
 
  A) Very Large Array Radio Telescope
  B) Chandra X-ray Telescope
  C) Herschel Infrared Telescope
  D) Hubble Space Telescope (UV and optical and some infrared)

[ryhom]

Answer to Question 1

D

Answer to Question 2

B

[rosent76]

Both answers were spot on, thank you once again

[ryhom]

Great! Please up vote