Huygen's construction or Huygen's principle
Each point on a primary wavefront serves as the source of spherical secondary wavelets that advance at the wavespeed for the propagating medium. The primary wavefront at some later time is the envelope of these wavelets.
The path taken by light traveling from one point to another is such that the time of travel is a minimum. That is, light travels along the path of least time.
Total internal reflection
Phenomenon which occurs when the incident angle is greater than the critical angle, so no refracted ray exists.
Angle of minimum deviation
The reflected angle at which the intensity of light reflected is a maximum.
When the electric field remains parallel to a line perpendicular to the direction of propagation.
complicated phenomenon that occurs in calcite and other noncubic crystals and in some stressed plastics, such as cellophane. In such cases, light is separated into two rays: the ordinary ray and the extraordinary ray.
the speed of light passing through the material is independent of the polarization of the light.
opposite of isotropic, biorefringent materials are because of their microscopic structure... speed of light changes in these materials due to the direction and propagation of the light.
the direction in which both the extraordinary and ordinary rays propagate at the same speed.
Plate whose thickness is such that a 90 degree phase difference exists between the waves of a particular wavelength when they emerge.
When the electric field vector rotates in a circle and has constant magnitude because the incident light was linearly polarized so that the electric field vector is at 45 degrees to the optic axis.
A particle of light with Energy E = hf = (hc)/λ where h = 6.626 x 10-34 J-s = 4.136 x 10-15 eV-s
Random emission where the photons emitted from two different atoms are not correlated
Scattering which occurs when the wavelength of incident light is large compared with the size of the atom.
Inelastic scattering or Raman scattering
when an incident photon that has just the right amount of energy is absorbed and the atom undergoes a transition to a more energetic state.
Stokes Raman scattering
when the energy of the scattered photon hf' is less than that of the incident photon
Anti-Stokes Raman scattering
when the energy of the scattered photon is greater than that of the incident photon.
when an atom absorbs a photon and making the transition to the more excited state
when an atom in an excited state spontaneously undergoes a transition to a less energetic state
when an atom is excited by ultraviolet light and emits visible light as it returns to its ground state by multiple transitions.
an excited state with a relatively long lifetime - of the order of milliseconds or occasionally seconds or even minutes
Materials that have very long-lived metastable states and emit light long after the original excitation
when the atom is initially in an excited state of energy EH and the energy of the incident photon is EH-EL where EH and EL are the energies of higher and lower energy states. The oscillating electromagnetic field associated with the incident photon can stimulate the excited atom, which then emits a photon in the same direction as the incident photon and in phase with it.
when the energy of the incident photon is much greater than the ionization energy. In this type of scattering, a photon is absorbed and another is emitted.
The phenomenon that causes your right hand to look like your left hand in the mirror - a right-to-left reversal.
blurriness caused by rays striking far from the axis and passing near the image point, but not through it.
Sign conventions for reflection
s is positive when the object is on the incident-light side of the mirror. s' is positive if the image is on the reflected-light side of the mirror. r, and thus f, is positive if the mirror is concave so the center of curvature is on the reflected-light side of the mirror.
Sign conventions for refraction
s is positive for objects on the incident-light side of the surface. s' is positive for images on the refracted-light side of the surface. r is positive if the center of curvature is on the refracted-light side.
Diverging or negative lens
a lens whose focal length is negative (any that is thinner in the middle than at the top and bottom)
First focal point
the focal point on the incident-light side of a converging lens, or on the refracted-light side of a diverging lens.
Second focal point
the focal point on the refracted-light side of a converging lens, or on the incident-light side of a diverging lens.
Principal rays for a thin lens
the rays you need to draw to determine the location of the final image formed from a thin lens.
drawn parallel to the axis; emerging ray is directed toward the second focal point of the lens
what a converging lens becomes when it is placed next to the eye with an object closer to the lens than its focal length.
the distance between the second focal point of the objective and the first focal point of the eyepiece in a microscope.
Phase difference due to reflection
If light traveling in one medium strikes the surface of a medium in which light travels more slowly, there is a 180° phase change in the reflected light.
alternating bright and dark bands caused by viewing a thin film of varying thickness with monochromatic light.
circular interference fringes resulting from viewing light reflected from an air film between a spherical glass surface and a plane of glass in contact.
m = 0, 1, 2... for two-slit interference maxima. m = 1, 2, 3... for two-slit interference minima.
Central diffraction medium
in single-slit diffraction, the area where most of the light intensity is concentrated.
Fraunhofer diffraction pattern
diffraction pattern that is observed at a point for which the rays from an aperture or an obstacle are nearly parallel
Rayleigh's criterion for resolution
when the critical angle of separation, αc = 1.22λ/D, separates two sources as seen through a circular aperture, the two sources will be seen as one source.
tool used for measuring the wavelength of light which consists of a large number of equally spaced lines or slits on a flat surface.
in a diffraction grating, each wavelength emitted by the source produces a separate image of the collimating slit