If a galaxy has a recessional velocity of 50,000 km/s, at what wavelength will you observe the H$\alpha$emission line? Note that the rest wavelength of the H$\alpha$ emission line is 656.3 nm.
A) 695.7 nm
B) 719.4 nm
C) 742.3 nm
D) 766.0 nm
E) 1750 nm

Question

Quizplus · Accepted Answer

The observed wavelength can be calculated using the formula:

Observed wavelength = Rest wavelength * (1 + velocity/c)

where c is the speed of light.

Plugging in the values, we get:

Observed wavelength = 656.3 nm * (1 + 50000 km/s / 3x10^5 km/s) = 742.3 nm

Therefore, the answer is C) 742.3 nm.

If a Galaxy Has a Recessional Velocity of 50,000 Km/s α\alphaα

If a Galaxy Has a Recessional Velocity of 50,000 Km/s $\alpha$