**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
centimeter).**De Broglie
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
their path. **Diffraction
Grating - **Material containing many parallel
lines very closely spaced that produces a light spectrum by
interference.
**Diffuse
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
into spectrum.
**Displacement - **Change in position. A vector
quantity.
**Dissonance - **Two or more sounds that, when
together, sound unpleasant.
**Distance - **Separation between two points. A
scalar quantity. **Diverging
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. |