Android Question How to automatically close the ads after click the ads from admob?

hello,
I used the rewarded ads and Interstitial Ads from AdMob.

In a test project, interstitialAd.show() is called .
the Interstitial ads displayed on screen.
here click on the Interstitial ads or click Home.
test app paused. and show browser or phone desktop.

but when i switching back to app, the Interstitial Ads is still show on screen.
not my test app image.

So， How to automatically close the ads after clicking the advertisement in admob?

like some other ads supply such as tencent ads:
when click ads, user can call a function ads.onDestroy to close ads.