Return correct data for a given date.

All,

I have two table one call Employee and the other table call Target Ratio. They are related via FK EmployeeID

tblEmployee
EmployeeID FirstName LastName
1 John Doe

tblTargetRatio
TargetRatioID EmployeeID EffectiveDate Ratio
1 1 1/1/2012 8
2 1 6/1/2012 5
3 1 9/1/2012 7

My question is how can I query tblTargetRatio table to return correct record for the following cases:

1 EmployeeID = 1 and Date = 03/12/2012 (Expecting Ratio = 8)
2 EmployeeID = 1 and Date = 10/10/2012 (Expecting Ratio = 7)
3 EmployeeID = 1 and Date = 08/12/2012 (Expecting Ratio = 5)

Thanks,
Alan