The Hγ line has a wavelength of 434.0 nm when observed in the laboratory. If the Hγ line appears in a stars spectrum at 434.5 nm, what is the radial velocity of the star
A)346 km/s away from the observer
B)346 km/s toward the observer
C)$1.3 × 10^8$ m/s away from the observer
D)$1.3 × 10^8$ m/s toward the observer
E)The radial velocity of the star cannot be determined from this information.

Question

Quizplus · Accepted Answer

The observed wavelength is longer than the rest wavelength, indicating the star is moving away from the observer due to the Doppler effect. The radial velocity can be calculated using the formula for Doppler shift in wavelengths, $v = c \times \frac{\Delta \lambda}{\lambda}$, where $v$ is the radial velocity, $c$ is the speed of light, $\Delta \lambda$ is the change in wavelength, and $\lambda$ is the original wavelength. Given the small change in wavelength, the velocity is positive, indicating motion away from the observer.

The Hγ Line Has a Wavelength of 434 1.3×1081.3 × 10^81.3×108

The Hγ Line Has a Wavelength of 434 $1.3 × 10^8$