# Tag Info

The width of a SN light curve is changed due to a time dilation between the source and the observer. If the source emits light with wavelength $\lambda_\text{em}$, it will be observed with wavelength $\lambda_\text{ob}$, so that its redshift is $$1 + z = \frac{\lambda_\text{ob}}{\lambda_\text{em}}.$$ We can also write everything in terms of frequencies ...