| convergent | Tending toward a common point. (05 Mar 2000) |
|---|---|
| Convergent Beam Electron Diffraction | <microscopy> An electron probe is tightly focused on a transmission electron microscopy specimen and the resulting pattern of diffracted electrons is observed. The patterns contains information on the crystal symmetry and atomic and electronic structure of the sample. Regions as small as 0.2 nm may be examined. Acronym: CBED (05 Aug 1998) |
| convergent evolution | The process where two unrelated structures in unrelated organisms evolve to perform similar functions. (The structures are called analogous structures.) For example: the wings of bats, birds, and insects evolved separately from each other but all are used to perform the function of flying. For another example: the complex eyes of vertebrates, cephalopods (squid and octopus), cubozoan jellyfish, and arthropods (insects, spiders, crustaceans) evolved separately, but all perform the function of vision. (09 Oct 1997) |
| convergent squint | Cross-eyed. (27 Sep 1997) |
| convergent strabismus | Cross-eyed. (27 Sep 1997) |
| anode rays | Those originating in a gas discharge tube and moving in a direction opposite to that of cathode ray's; made up of positively charged ions. Synonym: positive rays. (05 Mar 2000) |
| Becquerel rays | An obsolete term for radiations given off by uranium and other radioactive substances; these include alpha, beta, and gamma ray's. (05 Mar 2000) |
| gamma rays | Very powerful and penetrating, high-energy electromagnetic radiation of shorter wavelength than that of X-rays. They are emitted by a decaying nucleus, usually between 0.01 and 10 mev. They are also called nuclear X-rays. (12 Dec 1998) |
| parallel rays | Ray's parallel to the axis of an optical system. (05 Mar 2000) |
| marginal rays | In geometric optics, those ray's originating from the periphery. (05 Mar 2000) |
| paraxial rays | In geometric optics, those ray's focused at the principal point. (05 Mar 2000) |
| cathode rays | A stream of electrons emitted from the negative electrode (cathode) in a Crookes tube; their bombardment of the anode or the glass wall of the tube gives rise to X-ray's. (05 Mar 2000) |
| glass rays | Those formed by cathode ray's striking the wall of an X-ray tube. (05 Mar 2000) |
| cephalometric X-rays | <dentistry> An X-ray of the head that shows whether your teeth are aligned properly, and whether they are growing properly. (08 Jan 1998) |
| monochromatic rays | Light ray's or ionizing radiation of a very narrow band of wavelengths (ideally, of a single wavelength). Compare: photopeak, characteristic radiation. (05 Mar 2000) |