Final answer:
The Duke's use of caesura in lines 45-46 creates a pause or break in the poem, emphasizing certain words or phrases.
Step-by-step explanation:
The effect of the Duke's use of caesura in lines 45-46 is to create a pause or break in the flow of the poem. This pause emphasizes the words or phrases that come before and after the caesura, drawing attention to them.
For example, if the lines are:
'The Duke rode through the forest, *pause* his horse swift and strong',
the caesura in the middle of the second line would give emphasis to 'his horse swift and strong'. The pause allows the reader to contemplate the Duke's horse as an important aspect of the scene.