# Measuring black hole red shifting?

1. Nov 27, 2014

### Lamdbaenergy

I've been searching over this and I don't quite get it yet. I just heard about this "z" parameter for gravitational red shifting and I thought it'd be fun to apply into the scenario of a solar-mass black hole.
The equation I looked at was (1/(2GM/c^2r)^0.5) - 1 = z
So, like, does the z parameter just mean that you multiply the original wavelength by it or add it with the original wavelength? Does the z give you a shift in nanometers or meters? I'd really appreciate it if someone could give me a good understanding of this.

2. Nov 27, 2014

### Matterwave

z is usually defined as $z=\frac{\lambda_o-\lambda_e}{\lambda_e}=\frac{\lambda_o}{\lambda_e}-1$ where $\lambda_e$ is the emitted wavelength and $\lambda_o$ is the observed wavelength.