1--- a) An excited Hydrogen atom, (which is not moving) can emit cyan (blue-green) colored light with a wavelength of 4.86 x 10-9m. Suppose that the atom is in a star which is moving away at a speed of 0.03 c. You measure the wavelength of the same hydrogen "line", which will now be Doppler-shifted. What is this new wavelength? b) Given that blue light has wavelengths between 450 x 10-9m and 500 x 10-9m, and red light has wavelengths between 610 x 10-9m and approximately 700 x 10-9m, has the Hydrogen line from the receding star been shifted toward the blue or towards the red? 2--- As the universe expands, a galaxy which is at a distance of 5.0 x 106 pc, is moving away from you. What is the velocity of the galaxy relative to you? [You are given that Hubble's Constant is H = 73(km/s) / (106 pc). Note -- you do not need to know the value of a pc (parsec) to solve the problem because pc will cancel out if you do it right.] 3.--- a) The distance to Alpha Centauri (the nearest large star to Earth) is 4.37 Ly (Light Years). What is the distance in miles (given that one Ly = 5.88 x 1012 miles?) b) Present rocket ship speeds are roughly 100,000 miles per hour, which is the same as 8.766 x 108 miles per year. At this speed, and using the distance you calculated in (a), how many years would it take to travel to Alpha Centauri?
1--- a) An excited Hydrogen atom, (which is not moving) can emit cyan (blue-green) colored light with a wavelength of 4.86 x 10-9m. Suppose that the atom is in a star which is moving away at a speed of 0.03 c. You measure the wavelength of the same hydrogen "line", which will now be Doppler-shifted. What is this new wavelength?
b) Given that blue light has wavelengths between 450 x 10-9m and 500 x 10-9m, and red light has wavelengths between 610 x 10-9m and approximately 700 x 10-9m, has the Hydrogen line from the receding star been shifted toward the blue or towards the red?
2--- As the universe expands, a galaxy which is at a distance of 5.0 x 106 pc, is moving away from you. What is the velocity of the galaxy relative to you? [You are given that Hubble's Constant is H = 73(km/s) / (106 pc). Note -- you do not need to know the value of a pc (parsec) to solve the problem because pc will cancel out if you do it right.]
3.--- a) The distance to Alpha Centauri (the nearest large star to Earth) is 4.37 Ly (Light Years). What is the distance in miles (given that one Ly = 5.88 x 1012 miles?)
b) Present rocket ship speeds are roughly 100,000 miles per hour, which is the same as 8.766 x 108 miles per year. At this speed, and using the distance you calculated in (a), how many years would it take to travel to Alpha Centauri?
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