Final answer:
Diverging mirrors are often used for rear-view mirrors in vehicles because they provide a wider field of view and eliminate blind spots. However, the main disadvantage is that they offer a smaller field of view compared to flat mirrors.
Step-by-step explanation:
The main disadvantage of using diverging mirrors for rear-view mirrors in vehicles is that they provide a smaller field of view compared to flat mirrors. Diverging mirrors have a wider field of view, which allows drivers to see the rear of their vehicle while making turns and check for traffic gaps when merging. Additionally, diverging mirrors help to eliminate blind spots by providing a wider angle of view.