Checkbox with ng-model that reflect if another element is showed

I have an element checkbox, that I want to reset the value of ng-model when another element is not showed, example: set to false if another element is not showed in my view. ng-show only hide my checkbox, but not reflect in object of controller.

<select ng-model="item.myOption" convert-to-boolean>
  <option value="false" selected>Option false</option>
  <option value="true">Option true</option>
</select>
<input type="checkbox" ng-model="item.myChecked" ng-show="item.myOption">