Density - The amount of mass or number of
particles per unit volume. In cgs units mass density has units
of gm cm-3. Number density has units cm-3 (particles per cubic
Wavelength - Length of de Broglie wave of
particle; Planck’s constant divided by momentum of particle.
Decibel - Unit of sound level.
Dependent Variable - Variable that responds to change
in manipulated variable.
Derived Units - Unit of quantity that consists of
combination of fundamental units.
Destructive Interference - Superposition of waves resulting
in a combined wave with zero amplitude.
Diffraction - Bending of waves around object in
Grating - Material containing many parallel
lines very closely spaced that produces a light spectrum by
Reflection - Reflection of light into many
directions by rough object.
Dimensional Analysis - Checking a derived equation by
making sure dimensions are the same on both sides.
Diode - Electrical device permitting only
one way current flow.
Dispersion of Light - Variation with wavelength of
speed of light through matter resulting in separation of light
Displacement - Change in position. A vector
Dissonance - Two or more sounds that, when
together, sound unpleasant.
Distance - Separation between two points. A
Lens - Lens that causes light rays to
spread apart or diverge; usually a concave lens.
Dopants - Small quantities of material
added to semiconductor to increase electrical conduction.
Doppler Shift - Change in wavelength due to
relative motion of source and detector.
Dynamics - Study of motion of particles
acted on by forces.