Exam IV Vocabulary Flashcards
critical angle
the minimum angle of incidence inside a medium at which a light ray is totally reflected
refraction
the bending of an oblique ray of light when it passes from one transparent medium to another
diffraction
the bending of light that passes near the edge of an object or through a narrow slit, causing the light to spread
total internal reflection
the total reflection of light traveling within a denser medium when it strikes the boundary with a less dense medium at an angle larger than the critical angle
convex lense
converging
a lens that is thicker in the middle than at the edges and that refracts parallel rays to & fo
concave lense
diverging
a lens that is thinner in the middle than at the edges, causing parallel rays to diverge as if from a point
virtual image
an image formed by light rays that do not converge at the location of the image
real image
an image formed by light rays that converge at the location of the image. a real image, unlike a virtual image, can be displayed on a screen
huygen’s principle
every point on a wavefront may be considered the source of secondary wavelets that spread out in all directions with a speed equal to the speed of propagation of the wave
superposition
the overlapping and combining of waves
radioactivity
the sponatneous emission of energetic particles by an atomic nucleus
alpha ray
α-ray
a stream of alpha particles (helium nuclei) ejected by certain radioactive elements
beta ray
β-ray
a stream of electrons emitted during the radioactive decay of certain nuclei
gamma ray
γ-ray
high frequency electromagnetic radiation emitted by the nuclei of radioactive atoms
half-life
the time required for half the atoms in a sample of radioactive isotope to decay
electron
the negative particle in the outer part of the atom
rad
The acronym (radiation absorbed dose) for a unit of absorbed energy
rem
The acronym (roentgen equivalent man) for a unit used to measure the effect of ionizing radiation on humans
nuclear fission
the splitting of the nucleus of a heavy atom, such as uranium-235, into two smaller nuclei, accompanied by the release of much energy
nuclear fusion
the combination of light atomic nuclei to form heavier nuclei often with release of much energy
strong nuclear force
the force that attracts nucleons to each other within the atomic nucleus; a force that is very strong at close distances and greatly weakens as distance increases
radiation detectors
geiger + scintillation counters & cloud + bubble chambers
- geiger counter detects incoming radiation by a short pulse of current triggered when radiation ionizes a gas in the tube.
- scintillation counter indicates incoming radiation by flashes of light produced when charged particles or gamma rays pass through the counter.
- cloud chamber: charged particles moving through supersaturated vapor leaves trails
- bubble chamber: liquid hydrogen is heated under pressure in a glass and stainless steel chamber to a point just short of boiling.