convex lens

(noun)

A lens having at least one convex surface, such that light passing through it, may be brought to a focus.

Related Terms

Examples of convex lens in the following topics:

  • The Magnifying Glass

    • A magnifying glass is a convex lens that lets the observer see a larger image of the object being observed.
    • Since a magnifying glass uses its convex shape to focus light in a certain position, it can be used to converge the sun's radiation at the focus, causing hot spots.
    • A magnifying glass is a convex lens that lets the observer see a larger image of the object under observation.
    • 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.
    • A magnifying glass is a convex lens that lets the observer see a larger image of the object under observation.

  • Refraction Through Lenses

    • The word lens derives from the Latin word for lentil bean—the shape of which is similar to that of the convex lens (as shown in ).
    • The convex lens is shaped so that all light rays that enter it parallel to its axis cross one another at a single point on the opposite side of the lens.
    • Such a lens is called a converging (or convex) lens for the corresponding effect it has on light rays.
    • 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 Compound Microscope

    • A compound microscope is made of two convex lenses; the first, the ocular lens, is close to the eye, and the second is the objective lens.
    • It is made of two convex lenses: the first, the ocular lens, is close to the eye; the second is the objective lens.
    • shows a diagram of a compound microscope made from two convex lenses.
    • The first lens is called the objective lens and is closest to the object being observed.
    • The distance between the objective lens and the ocular lens is slightly shorter than the focal length of the ocular lens, fe.

  • Thin Lenses and Ray Tracing

    • 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. "
    • Shows how to draw the ray diagrams for locating the image produced by a concave lens and a convex mirror.

  • Aberrations

    • This aberration happens when the lens fails to focus all the colors on the same convergence point .
    • Since the index of refraction of lenses depends on color or wavelength, images are produced at different places and with different magnifications for different colors. shows chromatic aberration for a single convex lens.
    • 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 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:
    • Shows how to use the thin lens equation to calculate the image distance, image height and image orientation for convex lenses when the object distance is greater the the focal length (f).

  • The Lensmaker's Equation

    • A lens is biconvex (or double convex, or just convex) if both surfaces are convex.
    • If the lens is biconcave, a beam of light passing through the lens is diverged (spread); the lens is thus called a negative or diverging lens.
    • The signs of the lens' radii of curvature indicate whether the corresponding surfaces are convex or concave.
    • The sign convention used to represent this varies, but for our treatment if R1 is positive the first surface is convex, and if R1 is negative the surface is concave.
    • The signs are reversed for the back surface of the lens: if R2 is positive the surface is concave, and if R2 is negative the surface is convex.

  • Nearsightedness, Farsidedness, and Vision Correction

    • The lens provides the remaining power.
    • The image passes through several layers of the eye, but this happens in a way very similar to that of a convex lens.
    • The eye's lens is flexible, and changes shape.
    • The eye's ciliary muscles control the shape of the lens.
    • An image is formed on the retina with light rays converging most at the cornea and upon entering and exiting the lens.

  • 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.
    • Note the sign convention: a telescope with two convex lenses (f1 > 0, f2 > 0) produces a negative magnification, indicating an inverted image.
    • A convex plus a concave lens (f1 > 0 >f2) produces a positive magnification and the image is upright.
    • An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration.

  • Newton's Rings

    • The outer rings are spaced more closely than the inner ones because the slope of the curved lens surface increases outwards.
    • A spherical lens is placed on top of a flat glass surface.
    • As one gets farther from the point at which the two surfaces touch, the distance d increases because the lens is curving away from the flat surface .
    • Newton's rings seen in two plano-convex lenses with their flat surfaces in contact.
    • One surface is slightly convex, creating the rings.