Physics
Definitions
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Primary
Cell : A cell in which chemical action is not reversible
is called a primary cell. e.g. Voltaic Cell, Daniel Cell, Leclanche
Cell and dry Cell. |
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| Permanent
Magnets : Hardened steel and certain magnetic alloys (e.g.
cobalt steel, tungsten steel etc.) when magnetized retain
their magnetism indefinitely. Magnets made from such materials
are called permanent magnets. |
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| Plane
Wavefront : At a large distance from a source of any kind,
the wavefront will appear plane, Such a wavefront is called
plane wavefront. |
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Polarization
: The phenomenon of restricting the vibrations of a transverse
wave in a particular direction is called polarization of transverse
wave. |
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Polarization
of Light : The phenomenon of restricting the vibrations
of light in a particular plane is called polarization of light. |
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| Photons
: Radiation from a source is transmitted by tiny particles called photons. |
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| Packing
Fraction : The divergence of the nuclear mass from the
nearest whole number (i.e. its mass number A) per nucleon
is called packing fraction i.e. packing Fraction,
f = M - A / A where M = actual mass of nucleus, A
= mass number, As M - A is the mass defect, packing fraction
may also be expressed as f = ΔM / A = mass defect/ mass
number. |
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| Primitives
: The three sides a, b and c of the unit cell are known
as primitives or characteristic intercepts. |
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Polycrystal : A crystal solid which is made up of a large
number of monocrystals whose developed faces are joined together
is called polycrystal. |
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| p-Type
Semiconductor : When a small amount of trivalent impurity
is added to a pure semiconductor, it is called p-type semiconductor.
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| pn
Junction : When a semiconductor crystal (germanium or silicon)
is so prepared that one half is p-type and the other n-type,
the contact surface dividing the two halves is called a pn
junction. |
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| Planet
: A planet is heavenly body that the orbits the sun or
another star and shines only by the light that it reflects. |
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