• # question_answer A galaxy is moving away from an observe on the earth so that sodium light of wavelength $5892\overset{\text{o}}{\mathop{\text{A}}}\,$ is observed at $5896\overset{\text{o}}{\mathop{\text{A}}}\,$. The speed of galaxy is                                        A)  $306\,\,km/s$          B)  $204\text{ }km/s$                  C)  $185\,km/s$          D)  $158\text{ }km/s$

$v=C\frac{\Delta \lambda }{\lambda }$ $=3\times {{10}^{8}}\times \frac{(5896-5892)}{5892}$ $=0.00204\times {{10}^{8}}=204\,km/s$