Intensity Map - A color-coded map of radiation
intensity as a function of position. Different colors or shades
represent different intensities of observed radiation.
Ion - An atom that has lost or gained
one or more electrons and has become electrically charged as a
Ionization - The process by which ions are
produced, typically occurring by collisions with atoms or
electrons ("collisional ionization"), or by interaction with
electromagnetic radiation ("photoionization").
Ionosphere - The region of the Earth's upper
atmosphere containing a small percentage of free electrons and
ions produced by photoionization of the constituents of the
atmosphere by solar ultraviolet radiation. The ionosphere
significantly influences radiowave propagation of frequencies
less than about 30 MHz.
Isotope - One of two or more atoms having
the same number of protons in its nucleus, but a different
number of neutrons and, therefore, a different mass.
Ideal Mechanical advantage - In simple machine, the ratio of
effort distance to resistance distance.
Illuminance - Rate at which electromagnetic
wave energy falls on a surface.
Illuminated Object - Object on which light falls.
Image - Reproduction of object formed
with lenses or mirrors.
Impulse - Product of force and time
interval over which it acts.
Impulse-momentum Theorem - Impulse given to an object is
equal to its change in momentum.
Incandescent Body - Object that emits light because
of its high temperature.
Incident Wave - Wave that strikes a boundary
where it is either reflected or refracted.
Incoherent Light - Light consisting of waves that
are not in step.
Independent Variable - Variable that is manipulated or
changed in an experiment.
Index of Refraction - Ratio of the speed of light in
vacuum to its speed in a material.
Inelastic Collision - Collision in which some of the
kinetic energy is changed into another form.
Inertia - Tendency of object not to change
Inertial Mass - Ratio of net force exerted on
object to its acceleration.
Initial Velocity - Velocity of object at time t=0.
Instantaneous Acceleration - Acceleration at a specific time;
slope of tangent to velocity- time graph.
Instantaneous Position - Position of an object at specific
Velocity - Slope of the tangent to position-
Insulator - Material through which the flow
of electrical charge carriers or heat is greatly reduced.
Interference Fringes - Pattern of dark and light bands
from interference of light waves.
Interference of Waves - Displacements of two or more
waves, producing either large or smaller waves.
Internal Forces - Forces between objects within a
Semiconductor - Semiconductor in which conduction
is by charges due to host material, not impurities.
Inverse Relationship - Mathematical relationship between
two variables, x and y, summarized by the equation xy=k, where k
is a constant.
Radiation - Particles or waves that can
remove electrons from atoms, molecules, or atoms in a solid.
Isolated System - A collection of objects not acted upon by external
forces into which energy neither enters nor leaves.