// Create  new object of SPWebApplication & SPWebApplicationBuilder class
SPWebApplication newApplication;
SPWebApplicationBuilder webAppBuilder = new SPWebApplicationBuilder(SPFarm.Local);

// Set necessary values to webAppBuilder object

webAppBuilder.Port = portNo;
webAppBuilder.RootDirectory = new DirectoryInfo(D:projectsTestWebSite3030);
webAppBuilder.ApplicationPoolId = appPoolId;
webAppBuilder.ApplicationPoolUsername = appPoolUserName;
webAppBuilder.ApplicationPoolPassword = password;
webAppBuilder.CreateNewDatabase = true;
webAppBuilder.DatabaseServer = dbServerName; // DB server name
webAppBuilder.DatabaseName = dbName;// DB Name
if (isSQLAuth)
{
webAppBuilder.DatabaseUsername = dbUid; // dbUid is username of the DB sever
webAppBuilder.DatabasePassword = dbPwd; // dbpassword is password of the DB sever
}
webAppBuilder.UseNTLMExclusively = true;  // authentication provider for NTLM
webAppBuilder.AllowAnonymousAccess = isAnonymous; // anonymous access permission

// Finally create web application
newApplication = webAppBuilder.Create();
newApplication.Provision();

$ap = New-SPAuthenticationProvider
New-SPWebApplication -Name "Contoso Internet Site" -Port 443 -HostHeader sharepoint.contoso.com -URL "https://www.contoso.com" -ApplicationPool "ContosoAppPool" -ApplicationPoolAccount (Get-SPManagedAccount "DOMAINjdoe") -AuthenticationProvider $ap -SecureSocketsLayer

New-SPWebApplication -Name "Contoso Internet Site" -Port 443 -HostHeader sharepoint.contoso.com -URL "https://www.contoso.com" -ApplicationPool "ContosoAppPool" -ApplicationPoolAccount (Get-SPManagedAccount "DOMAINjdoe") -AuthenticationProvider $ap -SecureSocketsLayer