During the main part of the day, if there are ten a/c waiting to depart but only three due to land. The ten have to queue one behind the other and the 'landing' runway goes unused.
There are two fixed periods, 7-3 and 3-11 where one runway is designated for arriving and the other for departing. After 11 and up to 6am, one runway is used for both arrivals and departures amd the other is closed. However in practice, when the Southern runway is used for departures, a fair few arrivals are landed as well, as it's much easier for T4. I have rarely if ever seen the approach to the landing runway empty, even late at night there's generally four on the approach.