thick lens

(noun)

Lenses whose thicknesses are not negligible (i.e., one cannot make the simple assumption that a light ray is refracted only once in the lens).

Related Terms

Examples of thick lens in the following topics:

  • The Lensmaker's Equation

    • The lensmaker's formula is used to relate the radii of curvature, the thickness, the refractive index, and the focal length of a thick lens.
    • A lens whose thickness is not negligible is called a thick lens.
    • Instead the extent of the refraction must be dependent on the thickness of the lens.
    • The focal length of a thick lens in air can be calculated from the lensmaker's equation:
    • The above equation can be greatly simplified if the lens thickness d is very small compared to R1 and R2.

  • Thin Lenses and Ray Tracing

    • A thin lens is defined to be one whose thickness allows rays to refract, as illustrated in , but does not allow properties such as dispersion and aberrations.
    • An ideal thin lens has two refracting surfaces but the lens is thin enough toassume that light rays bend only once.
    • Another way of saying this is that the lens thickness is much much smaller than the focal length of the lens.
    • A thin symmetrical lens has two focal points, one on either side and both at the same distance from the lens.
    • The treatment of a lens as a thin lens is known as the "thin lens approximation. "

  • Aberrations

    • Types of aberrations vary due to the size, material composition, or thickness of a lens, or the position of an object.
    • This aberration happens when the lens fails to focus all the colors on the same convergence point .
    • Since violet rays have a higher refractive index than red, they are bent more and focused closed to the lens. shows a two-lens system using a diverging lens to partially correct for this, but it is nearly impossible to do so completely.
    • Spherical aberrations are a form of aberration where rays converging from the outer edges of a lens converge to a focus closer to the lens, and rays closer to the axis focus further.
    • The apparent effect is that of an image which has been mapped around a sphere, like in a fisheye lens.

  • The Compound Microscope

    • It is made of two convex lenses: the first, the ocular lens, is close to the eye; the second is the objective lens.
    • The first lens is called the objective lens and is closest to the object being observed.
    • The objective lens creates an enlarged image of the object, which then acts as the object for the second lens.
    • The distance between the objective lens and the ocular lens is slightly shorter than the focal length of the ocular lens, fe.
    • where m is total magnification, mo is objective lens magnification, me is ocular lens magnification.

  • Refraction Through Lenses

    • Such a lens is called a converging (or convex) lens for the corresponding effect it has on light rays.
    • The concave lens is a diverging lens, because it causes the light rays to bend away (diverge) from its axis.
    • The distance from the center of the lens to the focal point is again called the focal length f of the lens.
    • The more powerful the lens, the closer to the lens the rays will cross.
    • Compare the effect of a convex lens and a concave lens on the light rays

  • The Thin Lens Equation and Magnification

    • How does a lens form an image of an object?
    • A ray entering a converging lens parallel to its axis passes through the focal point F of the lens on the other side.
    • The third ray passes through the nearer focal point on its way into the lens and leaves the lens parallel to its axis (rule 4).
    • The thin lens equation is:
    • Ray tracing is used to locate the image formed by a lens.

  • Phase-Contrast Microscopy

    • Unaltered light hits the phase ring in the lens and is excluded.
    • This tool works best with a thin specimen and is not ideal for a thick specimen.

  • Combinations of Lenses

    • A compound lens is an array of simple lenses with a common axis.
    • In contrast to a simple lens, which consists of only one optical element, a compound lens is an array of simple lenses (elements) with a common axis.
    • An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration.
    • In the most common type (shown in ), the positive power of the crown lens element is not quite equaled by the negative power of the flint lens element.
    • Calculate focal length for a compound lens from the focal lengths of simple lenses

  • Protists as Human Pathogens

    • Trypanosoma brucei, the parasite that is responsible for African sleeping sickness, confounds the human immune system by changing its thick layer of surface glycoproteins with each infectious cycle .
    • In this light microscopic image taken using a 100× oil immersion lens, the ring-shaped P. falciparum stains purple.

  • The Magnifying Glass

    • A magnifying glass is a convex lens that lets the observer see a larger image of the object being observed.
    • A magnifying glass is a convex lens that lets the observer see a larger image of the object under observation.
    • The lens is usually mounted in a frame with a handle, as shown below .
    • The highest magnifying power is obtained by putting the lens very close to the eye and moving both the eye and the lens together to obtain the best focus.
    • When the lens is used this way, the magnifying power can be found with the following equation: