Property 4: Refraction
sin(?a) = ?a/x and sin(?w) = ?w/x
eliminate x: ?a/sin(?a) = ?w/sin(?w)
and use: ?f = v (or ? = v/f) to get
f sin(?a) / va = f sin(?w) / vw
NOTE: since ?w < ?a, need vw < va
which is opposite to the prediction of the particle theory but agrees with wave prediction of Property 1 on speed!