Doppler shifted hydrogen absorption lines are seen in the spectrum of a star. The hydrogen line at 656.28 nm is seen to be shifted to 656.08 nm. How large is the fractional shift in wavelength?

Question

Quizplus · Accepted Answer

The fractional shift in wavelength can be calculated using the formula:

Δλ/λ = Δv/c

where Δλ is the change in wavelength, λ is the original wavelength, Δv is the speed of the object along the line of sight, and c is the speed of light.

In this case, Δλ = 656.28 nm - 656.08 nm = 0.20 nm

Substituting this value into the formula:

Δλ/λ = 0.20 nm/656.28 nm = 3.05 × 10-4

Therefore, the fractional shift in wavelength is about 0.0003, which corresponds to choice B.

Doppler Shifted Hydrogen Absorption Lines Are Seen in the Spectrum