Equation Icon  4 πa30r30ρ0 M = ------1--2-3, (169 ) 3(1 + 4kr0) --ρℰ0a40r40--- Q = (1 + 1kr2)4, (170 ) 4 0 ----kr20---- E = − (1 + 1kr2 )2 > − 1. (171 ) 4 0