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 zoom lens is a mechanical assembly of lens elements for which the focal length (and thus angle of view) can be varied, as opposed to a fixed focal length (FFL) lens (see prime lens).A true zoom lens, also called a parfocal lens, is one that maintains focus when its focal length changes.A lens that loses focus during zooming is more properly called a varifocal lens.enses in the latter group of zoom lenses, sometimes referred to as normal zooms, have displaced the fixed focal length lens as the popular one-lens selection on many contemporary cameras. The markings on these lenses usually say W and T for Wide and Telephoto.