We present a scheme in which we investigate the two-slit experiment and the the principle of complementarity. PACS: 03.65.Ud; 03.67.Mn; 32.80.-t; 42.50.-p Keywords: principle of complementarity, cavity QED. The investigation of the double slit experiment in which we have two micromaser cavities, each one associated with one of the slits, was proposed before by Scully and Walther in a series of very interesting articles where they investigate the principle of complementarity and the uncertainty principle [1, 2, 3] and they conclude that the principle of complementarity is more fundamental than the uncertainty principle. Recently we have published an article [4] where we have got the same conclusion. In this article we proceed with a further investigation of the subject studied in [4]. As in [4] first we are going to consider a screen with two slits SL1 (at ζ1) and SL2 (at ζ2) with two cavities C1 and C2 behind respectively each slit, through which fly Rydberg atoms of relatively long radiative lifetimes [5], and first prepared in coherent state |α〉1 and |α〉2 [3, 6] respectively and later we consider the cavities prepared in an even coherent state |+〉1 and an odd coherent state |−〉2 respectively, where | ±〉k = | α〉k ± | −α〉k (1) [7]. We also assume perfect microwave cavities, that is, we neglect effects due to decoherence. Let us consider a three-level lambda atom interacting with the electromagnetic field inside a cavity where the upper and the two degenerated lower states are |a〉, |b 〉 and |c 〉 respectively, and for which the |a 〉 ⇀ ↽ |c 〉 and |a 〉 ⇀ ↽ |b 〉 transitions are in the far from resonance interaction limit. The time evolution operator U(t) for the atom-field interaction in a cavity Ck is given by [8] U(τ) = −e iϕa † k ak |a〉〈a | + 1