- axis of a polarizing filter
- the direction along which the filter passes the electric field of an EM wave

- birefringent
- crystals that split an unpolarized beam of light into two beams

- Brewster’s angle
- ${\theta}_{\text{b}}={\text{tan}}^{-1}\left(\frac{{n}_{2}}{{n}_{1}}\right),$ where ${n}_{2}$ is the index of refraction of the medium from which the light is reflected and ${n}_{1}$ is the index of refraction of the medium in which the reflected light travels

- Brewster’s law
- $\text{tan}\phantom{\rule{0.25em}{0ex}}{\theta}_{\text{b}}=\frac{{n}_{2}}{{n}_{1}}$, where ${n}_{1}$ is the medium in which the incident and reflected light travel and ${n}_{2}$ is the index of refraction of the medium that forms the interface that reflects the light

- coherent
- waves are in phase or have a definite phase relationship

- confocal microscopes
- microscopes that use the extended focal region to obtain three-dimensional images rather than two-dimensional images

- constructive interference for a diffraction grating
- occurs when the condition $d\phantom{\rule{0.25em}{0ex}}\text{sin}\phantom{\rule{0.25em}{0ex}}\theta =\mathrm{m\lambda}\phantom{\rule{0.25em}{0ex}}\text{(for}\phantom{\rule{0.25em}{0ex}}m=\text{0,}\phantom{\rule{0.25em}{0ex}}\text{1,}\phantom{\rule{0.25em}{0ex}}\text{\u20131,}\phantom{\rule{0.25em}{0ex}}\text{2,}\phantom{\rule{0.25em}{0ex}}\text{\u20132,}\phantom{\rule{0.25em}{0ex}}\dots )$ is satisfied, where $d$ is the distance between slits in the grating, $\lambda $ is the wavelength of light, and $m$ is the order of the maximum

- constructive interference for a double slit
- the path length difference must be an integral multiple of the wavelength

- contrast
- the difference in intensity between objects and the background on which they are observed

- destructive interference for a double slit
- the path length difference must be a half-integral multiple of the wavelength

- destructive interference for a single slit
- occurs when $D\phantom{\rule{0.25em}{0ex}}\text{sin}\phantom{\rule{0.25em}{0ex}}\theta =\text{m\lambda},\phantom{\rule{0.25em}{0ex}}\text{(for}\phantom{\rule{0.25em}{0ex}}m=\text{1,}\phantom{\rule{0.25em}{0ex}}\text{\u20131,}\phantom{\rule{0.25em}{0ex}}\text{2,}\phantom{\rule{0.25em}{0ex}}\text{\u20132,}\phantom{\rule{0.25em}{0ex}}\text{3,}\phantom{\rule{0.25em}{0ex}}\dots )$, where $D$ is the slit width, $\lambda $ is the light’s wavelength, $\theta $ is the angle relative to the original direction of the light, and $m$ is the order of the minimum

- diffraction
- the bending of a wave around the edges of an opening or an obstacle

- diffraction grating
- a large number of evenly spaced parallel slits

- direction of polarization
- the direction parallel to the electric field for EM waves

- horizontally polarized
- the oscillations are in a horizontal plane

- Huygens’s principle
- every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wavefront is a line tangent to all of the wavelets

- incoherent
- waves have random phase relationships

- interference microscopes
- microscopes that enhance contrast between objects and background by superimposing a reference beam of light upon the light emerging from the sample

- optically active
- substances that rotate the plane of polarization of light passing through them

- order
- the integer $m$ used in the equations for constructive and destructive interference for a double slit

- phase-contrast microscope
- microscope utilizing wave interference and differences in phases to enhance contrast

- polarization
- the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave

- polarization microscope
- microscope that enhances contrast by utilizing a wave characteristic of light, useful for objects that are optically active

- polarized
- waves having the electric and magnetic field oscillations in a definite direction

- Rayleigh criterion
- two images are just resolvable when the center of the diffraction pattern of one is directly over the first minimum of the diffraction pattern of the other

- reflected light that is completely polarized
- light reflected at the angle of reflection ${\theta}_{\text{b}}$, known as Brewster’s angle

- thin film interference
- interference between light reflected from different surfaces of a thin film

- ultraviolet (UV) microscopes
- microscopes constructed with special lenses that transmit UV rays and utilize photographic or electronic techniques to record images

- unpolarized
- waves that are randomly polarized

- vertically polarized
- the oscillations are in a vertical plane

- wavelength in a medium
- ${\lambda}_{\text{n}}=\lambda /n$, where $\lambda $ is the wavelength in vacuum, and $n$ is the index of refraction of the medium