# Black hole falling observer blueshifted light

As per chapter 7, figure 8 Link from Exploring Black Holes, 2nd Edition for a falling (rain frame) observer dt(reception) of light pulses sent from far away one second apart is greater than one second. So outside light should appear red shifted to a rain observer, which is not the real case. Light appears blue shifted to a rain observer after he crosses the horizon. So, what am I missing?

• I don't think you are missing anything. It does appear redshifted Commented Oct 14, 2021 at 3:16
• Well, the same book, chapter 12 says it does not. It also says, just before reaching the singularity the energy of the blue shifted light might kill you. eftaylor.com/exploringblackholes/… Commented Oct 14, 2021 at 3:54

$$\frac{f}{f_0} = \frac{1}{1 + \sqrt{\frac{r_s}{r}}}$$
The value $$b$$ on the graph is the impact parameter. When $$b = 0$$ the light is coming from directly behind you and you and the light just fall in a straight line directly into the black hole. In this case you see the light redshifted all the way to your final doom at the singularity at the centre. Value of $$b \ne 0$$ means the light is not coming from directly behind you so it can be deflected by the black hole and meet you from a different direction. Whether you see this light as blue or red shifted depends on the direction in which it meets you.