You see a galaxy in which the H$\alpha$ 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

The redshift (z) can be calculated using the formula:
z = (observed wavelength - rest wavelength)/rest wavelength

For the given hydrogen line, z = (756.3 nm - 656.3 nm)/656.3 nm = 0.152
This means that the galaxy is moving away from us at a speed of 0.152 times the speed of light.

To calculate the observed wavelength of the helium line, we can use the formula:
observed wavelength = (1 + z) * rest wavelength

Plugging in the values, we get:
observed wavelength = (1 + 0.152) * 1,083 nm = 1,248 nm

Therefore, the best choice is C.

You See a Galaxy in Which the H α\alphaα Line (Rest Wavelength= 656

You See a Galaxy in Which the H $\alpha$ Line (Rest Wavelength= 656