Discuss the impact of $broadcast and $emit on event handling in complex AngularJS applications.

$broadcast and $emit are methods in AngularJS for event handling. $broadcast dispatches events downwards to child scopes, while $emit dispatches events upwards to parent scopes. Understanding the impact of these methods on event flow is crucial, especially in complex AngularJS applications with nested scopes. Developers need to choose the appropriate method based on the desired event propagation direction.