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- Homework Statement
- One wavelength in the hydrogen spectrum of light from Ursa Majoris is 486.112 nm. In the laboratory, this spectral line is found to have a wavelength of 486.133nm. Determine the velocity of Ursa Majoris relative to Earth. (speed of light = 3.0 x 10^8 m/s)

- Relevant Equations
- doppler effect equation

The solution on my textbook is

I'm able to calculate the magnitude of velocity (13000m/s), but i don't understand why thus is blue-shifted? Since in the lab, the light's wavelength observed is slightly higher than light from Ursa Majoris. So my thought is

**13000m/s toward Earth as the light is blue-shifted**I'm able to calculate the magnitude of velocity (13000m/s), but i don't understand why thus is blue-shifted? Since in the lab, the light's wavelength observed is slightly higher than light from Ursa Majoris. So my thought is

**red-shift and move away from earth.**Any any explanation?