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.
A lens with one convex and one concave side is convex-concave or meniscus. It is this type of lens that is most commonly used in corrective lenses. If the lens is biconvex or plano-convex, a collimated beam of light passing through the lens converges to a spot (a focus) behind the lens.hen the thickness of the lens is not much smaller than S 1 and S 2 or there are multiple lens elements (a compound lens), one must instead measure from the object and image to the principal planes of the lens.