The following examples use the Orders table to show how the positive and negative unary operators function. When a positive unary operator is set against a negative value, the returned value is negative (positive_value * negative_value = negative_value). When a negative unary operator is set against a negative value, the returned value is positive (negative_value * negative_value = positive_value). Copy. SELECT (DATEPART(day, Order Date) - DATEPART(day, Shipped Date)) FROM Orders WHERE OrderID = '10248' -- Without a unary operator, the value returned is '-12'.
Inmersion oil does not increase magnification. Inmersion oil is needed at high magnifications. Why? High magnifications come with high numerical appertures (although one can have a low-magnification high-numerical apperture objective). High numerical appertures are required to capture more light and improve resolution.
Although the objective featured in Figure 1 is designed to operate utilizing oil as the imaging medium between the objective front lens and specimen, other objectives have front lens elements that allow them to be use either in air or immersed in water, glycerin, or a other specialized hydrocarbon-based oils.