Fundamentals of Materials Science Flashcards
what is light?
- electromagnetic radiation resulting in changes of the state of electron cover
- includes ultraviolet, infrared, and x-ray radiation
what is dual character?
- stream of material particles
- photons widespreading as electromagnetic waves
what is visible light?
- has wavelength in a range from 380-760nm
- frequency range of 405-790THz
what happens when light is refracted by a prism?
the dispersion causes the separation of colors
white light is polychromatic. what does that mean?
it is a mixture of wavelengths
how are hue, value, and chroma determined?
reflected light intensity and combined intensities of wavelengths presented in incident and reflected light
what is reflection and brightness?
- reflection: either specular or diffuse, depending on the nature of the interface
- brightness: color property, expressed mainly in metals; depends on quality of reflected light. high brightness occurs when nearly all incident light is reflected
how can mirror-like reflection of ceramics construction occur?
opaque layer is backed by temperature higher than recommended
what is refraction?
change in direction of a wave due to change in its speed
what is absorption?
the property of material to let light pass through it
what is opacity?
object does not let incident light pass through it
what is the difference between transparency and translucency?
- in transparency, nearly all light passes through an object
- in translucency, only some light passes through an object
what is metamerism?
properties of materials to appear to have different colors when illuminated by different light sources
what is a metameric pair?
a pair of objects whose colors match under a certain illumination, but do not match if illumination conditions are changed
what is opalescence?
- origination of a rainbow inside a material with little opacity due to the interference of light waves owing to the inside defects and microstructural inhomogeneity
- teeth opalescence is the result of the interaction of light with enamel prisms - refraction, reflection, and interference
what is luminescence?
property of materials to absorb energy and emit it as visible light
what are the 2 types of luminescence?
- fluorescence: emission of light by a substance that has absorbed light of other electromagnetic radiation of a different wavelength
- phopshorescence: does not immediately re-emit the radiation it absorbs
describe the VITA classical A1-D4 shade guide
- A1-A4: reddish brown
- B1-B4: reddish-yellowish
- C1-C4: greyish shades
- D1-D4: reddish grey
chroma increases and value decreases as shades move from 1-4
describe the chromascop shade guide
- 5 color groups: 100, 200, 300, 400, 500
- increase in chroma and decrease in value and shade numbers increase
what is the scattering coefficient?
the fraction of incident light flux lost by reversal of direction in an elementary layer
what is the absoprtion coefficient?
the fraction of incident light flux lost by absorption in an elementary layer
what is light reflectivity?
the light reflectance of a material of infinite thickness
what is masking ability?
- dental restorations are often used to restore esthetic problems
- the ability of masking depends on optical constants and thickness of the dental materials used
why is temperature important in dentistry?
temperature produced during procedures can affect other tissues and produce pain or irreversible pulpitis
name 3 transition temperature techniques
- differential thermal analysis (DTA)
- thermo-mechanical analysis (TMA)
- dynamic mechanical analysis (DMA)
what is the heat of fusion?
the heat required to convert 1g of material from solid to liquid state at the melting temperature
what is thermal conductivity?
the quality of heat per second passing through a body 1cm thick with cross section of 1cm2 when the temperature difference is 1*C
what is specific heat?
the quality of heat needed to raise the temperature of 1g of a substance by 1*C
what is thermal diffusivity?
a measure of transient heat-flow
what is the coefficient of thermal expansion?
the change in length per unit length of material for a 1*C change in temperature
what is zeta-potential?
the potential difference existing between the surface of a solid particle immersed in a conducting liquid and the bulk of the liquid
