Galilean relativity – states that the laws of mechanics are valid in all inertial frames

Galilean telescope – a telescope in which the eyepiece is a diverging lens, producing an erect image (see figure 23.9)

Galvanometer – an instrument used to measure electric current

gamma rays – short-wavelength electromagnetic waves

Gauss's law for magnetism – the net magnetic flux through any (real or imaginary) closed surface is zero

Gauss’s law for electrostatics – the net electric flux through any (real or imaginary) closed surface is directly proportional to the net electric charge enclosed within that surface

Gaussian surface – a surface used to calculate the electric field from Gauss's law

General theory of relativity – states that all physical laws can be formulated so as to be valid for any observer, regardless of the observers motion

Generators – machines that convert mechanical energy into electrical energy

Gradient-index lens – a lens in which the index of refraction decreases as a function of distance from the optical axis

Gravity –the pull on all bodies in the earth’s sphere toward the earth’s center

Gravitational field strength – the gravitational force per unit mass on a small test mass

Gravitational potential energy - the potential energy due to the height of an object above some reference level.

Ground potential – in an electrical circuit, the point (or points) in the circuit that is maintained with a zero potential difference with respect to the Earth

Ground state – the lowest energy of a system