(2.25) The spy watched the man with the binoculars.
With a sentence like (2.25) you should find that there is a stronger break (longer pause, larger change in pitch) when the prepositional phrase (with the binoculars) tells you how the spy watched the man, than when it tells you which man the spy watched (the man who was holding the binoculars). For the sentences you have devised, you should find similar differences.
(2.26) While John was reading the book fell off his lap.
(2.27) While John was reading the book it fell off his lap.
For sentence pairs like (2.26) and (2.27) the stronger break should be where you would punctuate these sentences with a comma, so after reading in (2.26) but after book in (2.27), and in equivalent places for your sentences.