(1) hν= hc/λ =13.6×1.6×10^(-19)=2.2×10^(-18) J
λ=6.63 ×10^(-34)×3×108 /2.2×10^(-18)=9.1×10^(-8) m
(2)hν0 =hc/λ=w=3.6×1.6×10^(-19) =5.76×10^(-19)J
λ极=6.63 ×10^(-34)×3×10^8 /5.76×10^(-19) =3.5×10^(-7)m
(3)E(A极)-E(K极) = eU ,E(K极)=hν-w
E(A极)=eU+ E(K极)=eU+hν-w=20+13.6-3.6=30eV