Explicitly Closing Modal Popup Extender On Page Redirection

I have a modal pop up with Ok and Cancel buttons.

On 'OK', I redirect to a new page that opens in a new tab. and On Cancel I close the pop up.I have the requirement to close the pop up after the user hits 'ok' and a new page is opened. But when I see the old page, the pop up is still open.

I have used the .Hide() method after Response.Redirect but it doesn't works.

Please advise.