What is the relationship between opportunity cost and the production possibilities frontier (PPF)?

Opportunity cost is the value of the next best alternative foregone when a choice is made. The production possibilities frontier (PPF) shows the maximum possible combinations of goods that can be produced with given resources. The relationship between opportunity cost and the PPF is that as you move along the PPF and produce more of one good, the opportunity cost of producing that good increases because resources are being shifted away from producing other goods.