angularjs check box validation

HTML

<div data-ng-controller="myController">
    <form data-ng-submit="validate()">
      
                <label>Message to:</label>
                <span class="checkbox-group">
                <input type="checkbox" name="mobile" data-ng-model="formData.mobile" />
                 <label for="mobile">Mobile</label>
                 </span>
                 <span class="checkbox-group">
                 <input type="checkbox"    name="email" data-ng-model="formData.email" />
                 <label for="email">Email</label>
                 </span>
           
        <input type="submit" value="Submit" />
    </form>
</div>

JavaScript

function myController( $scope ){
    $scope.formData = {
        mobile : false, //initialize them to false, since by default they are undefined
        email : false       
    }
    $scope.validate = function(){
        if($scope.formData.mobile == false || $scope.formData.email == false)
        {
            alert('You\'ve not checked \'em all!')
        }
        else{
            alert('You\'ve checked \'em all!')
        }
    }
}