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.
Let's re-calculate the yield of the bond in our first example, which matures in 30 months and has a coupon payment of $5: The adjusted current yield of 6.84% is higher than the current yield of 5.21% because the bond's discounted price ($95.92 instead of $100) gives the investor more of a gain on the investment.