List of sites under Web App with Last modified date in SharePoint using PowerShell

Add-PSSnapin Microsoft.sharepoint.powershell -ErrorAction SilentlyContinue
$Webapp = "http://2010.ajtech.com"
$site = Get-SPSite -webapplication $Webapp -Limit All
$site | Get-SpWeb -Limit All |Select-Object -Property LastItemModifiedDate, URL | Export-Csv -path C:\siteslistlastmodified.csv