Yes, magnetic fields will certainly pass
through glass. You can even perform a simple
experiment to verify this: take two permanent
magnets, place them on either side of a glass jar,
and feel how they attract to each other. That
attraction indicates that the magnetic field is
propagating through the glass. If the magnets are
strong enough, the magnets will even attract each
other through your own hand! In fact, magnetic
fields will pass through most ordinary materials,
like wood, concrete, Teflon, copper, or water.
All materials can be classified by how they will
interact with magnetic fields: (1) diamagnetic
materials will create an induced magnetic field
that opposes the applied magnetic field, (2)
paramagnetic materials will create an induced
magnetic field that will attract toward the source
of the applied magnetic field, and (3)
ferromagnetic materials are the strong permanent
magnets that we encounter in everyday life.
The strength of an applied magnetic field as it
propagates through a material will depend on the
strength of the applied magnetic field, the
specific type of intervening material, and the
thickness of the material. Superconductors—such as
lead, tin, and mercury—are the special class of
materials that will not allow any magnetic field
to pass through it. Superconductors can be used to
levitate other magnets, which allow engineers to
build high-speed magnetic levitating trains.
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