You see a galaxy in which the Hα line (rest wavelength = 656.3 nm)is observed at a wavelength of 756.3 nm.What would be the observed wavelength of a particular helium line,which has a rest wavelength of 1,083 nm?
A)1,083 nm
B)1,183 nm
C)1,248 nm
D)1,440 nm
E)3,142 nm

Question

Quizplus · Accepted Answer

Using the formula λ_observed = (1+z)*λ_rest, where z is the redshift, we can solve for the redshift of the galaxy:
756.3 nm = (1+z)*656.3 nm
z = 0.151
Next, we can use this redshift to find the observed wavelength of the helium line:
λ_observed = (1+z)*λ_rest
λ_observed = (1+0.151)*1083 nm
λ_observed = 1248 nm
Therefore, the observed wavelength of the helium line would be 1,248 nm, which is choice C.

You See a Galaxy in Which the Hα Line (Rest