$3.$ If an image has a contrast of $1,$ what will be the spatial resolution in the frequency?

 $5.$ If x$-$ray photons with I$0$ of $10$ W$/$m$2$ of energy $50$ keV travels through $5$ cm of muscle: $($a$)$ what will the intensity of the photon be at the exit of the muscle? $($b$)$ If it then travels another $10$ cm in air before reaching the detector, what will the intensity of the photon be that is detected?