\magnification=\magstep2

$$
f_{\lambda}(\lambda) \quad = \quad {\rm ergs / cm^2 / s / Angstrom}
$$

$$
N \quad = \quad {  \int  { 
                           { {f_{\lambda}(\lambda) \thinspace T(\lambda)}}
                                \over{hc/{\lambda}} } 
                     d{\lambda}  } \quad\quad {\rm photons / cm^2 / s}
$$

$$
N(z) \quad = \quad   {\int {
                           { {f_{\lambda}( {{\lambda}\over{1 + z}} )
                              \thinspace  T(\lambda) }
                              \over {hc/{\lambda}} }
                     d{\lambda}  } }  
                      \quad\quad {\rm photons / cm^2 / s}
$$




\bye
