Online Physics Glossary 
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Word 
Meaning 
Remarks 
Halflife 
Length of time for half of a sample of radioactive material to decay.


Harmonics 
Frequencies produced by musical instrument that are multiples of fundamental tone.


Heat 
Quantity of energy transferred from one object to another because of a difference in temperature.


Heat engine 
Device that converts thermal energy to mechanical energy.


Heat of fusion 
Quantity of energy needed to change a unit mass of a substance from solid to liquid state at the melting point.


Heat of vaporization 
Quantity of energy needed to change a unit mass of a substance from liquid to gaseous state at the boiling point.


Heavy water 
Deuterium oxide used mainly in CANDU nuclear reactors.


Heisenberg uncertainty principle 
The more accurately one determines the position of a particle, the less accurately the momentum can be known, and vice versa.


Hertz 
Unit of frequency equal to one event or cycle per second.


Hole 
Absence of an electron in a semiconductor.


Hooke’s law 
Deformation of an object is proportional to force causing it.


Huygens’ wavelets 
Model of spreading of waves in which each point on wavefront is source of circular or spherical waves.


Hydraulic system 
Machines using fluids to transmit energy.


Hyperbola 
Mathematical curve that describes an inverse relationship between two variables.


Hypotenuse 
Side opposite the right angle in a triangle.



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