\magnification=\magstep2

$$
   {\rm central\ blob\ radius\ }  \theta =  1.22 \thinspace 
              { {\lambda}\over{D} } 
              \thinspace \thinspace {\rm radians }
$$

$$
   {\rm central\ blob\ radius\ }  \theta =   70 
            \thinspace  { {\lambda}\over{D} } 
            \thinspace \thinspace {\rm degrees }
$$


$$
    \theta = { v * (\Delta t) }
$$


$$ 
  L  =  4 \pi R^2 \sigma T^4
$$

$$ 
  R  =  \sqrt { {L} \over {4 \pi \sigma T^4} } 
$$






\bye
