Question

Consider a spiral galaxy that is moving directly away from Earth with a speed V=3.24*10^5 at its center. The galaxy is also rotating about its center such that points in the spiral arms are moving with a soeed V=5.750*10^5m/s relative to the center. If light with a frequency of 7.308*10^14Hz is emitted in both arms of the galaxy, what frequency is detected by astronomers observing the arm that is moving (a) toward and (b) away from Earth? Please break down steps.

Answer 1

Given spiral galaxy moving away from the earth a speedv 3.24x103 m/s Spiral ams are moving with a speed-v 5.75 x105 m/s Frequency of the light-f 7.308 x1014 Hz The spiral galaxy is moving away. So, the velocity "u" taken as negative The Doppler shift is a)the astronomers observing that ams that are moving towards As the arm is moving towards the earth and the galaxy is moving away from the earth therefore the resultant velocities is the velocity of the galaxy minus the velocity of the arm (3.24x10)-(5.75x 10) 3x108 -(7.308 x104)1 7.314x104 Hz b) As the arm is moving away from the earth and the galaxy is moving from the same direction. The resultant velocity is the velocity of the galaxy plus the velocity of the arm (3.24x10)+(5.75x10) 3x10 (7.308x104)1- 7.286x104 Hz