A photocell is any of a wide range of sensors that react based on the presence of light or electromagnetic energy. They can be found in many different forms, from solar panels that use light to generate electricity, to photoresistors, which shift in resistance based on how much light is present.
Bond prices and yields are like a seesaw: when bond yields go up, prices go down, and when bond yields go down, prices go up. In other words, a move in the 10-year Treasury yield from 2.2% to 2.6% indicates negative market conditions, while a move from 2.6% to 2.2% indicates positive market performance.
[VIDEO] Understanding Bond Yields. The first, and most important, concept you need to understand when discussing bond yields is that bond prices and bond yields have an inverse correlation. Picture a seesaw with bond prices on one side and bond yields on the other side. When bond prices are going up, bond yields are going down.