We use your earnings and work. history to determine your eligibility. for retirement or disability benefits. or your familyâs eligibility for. survivors benefits when you die. In 2016, you receive one credit for. each $1,260 of earnings, up to the. maximum of four credits per year. Each year the amount of earnings. needed for credits goes up slightly as. average earnings levels increase.
Immersion oil should only be used if you have an immersion oil lens. The lens will actually have oil, immersion or HI (homogeneous immersion) printed on it. Immersion oil is best for viewing samples that are dead or are not moving and no thicker than a few micrometers.
There are two main types of lenses: convex and concave. Convex lenses often get all the credit. They are the type of lens responsible for magnification and are the most common lens used in photography and other common applications. Concave lenses, though, serve an important role as well. A concave lens is any lens that has an inward curve in the middle.