Online Physics Glossary 
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Word 
Meaning 
Remarks 
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.



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