Do I get billed when an Azure App Service app didn't get any request the last 30 minutes or when not accessed for several hours?

For example (not real yet): I have an application deployed to Azure App Service. It is running on a B1 plan with 3 instances. Say that costs 0.05 USD / hour.

During the day, that app runs (gets continous requests) for 10 hours. So that's 0.5 USD for sure.

For the rest of the day, it doesn't receive any request.

Will I be billed the entire day, because the app is just being available? Or wil I be billed only for the time the application is actually being requested (so 10 hours plus probably the 20 minute ready time where the app doesn't go idle)?

I can't find anything about that subject. Maybe I'm searching the wrong way, maybe there isn't that much information available to answer this question. So I hope somebody here can point me to an article that gives (a way to) the answer I'm searching for, or maybe somebody can simply answer the question here?

Will I be billed the entire day, because the app is just being available?

Yes, you will be billed for the entire day because Microsoft has provisioned resources for you. It doesn't matter if you utilize those resources or not (Web App not getting any requests in your case).

You may find this link helpful: https://azure.microsoft.com/en-us/pricing/details/app-service/windows/#faq (Especially "How much does my App Service plan cost").