AQA • 8463 • 781 key terms
Absolute zero
The lowest possible temperature, equal to or , above which all bodies continuously emit infrared radiation.
From: Emission and absorption of infrared radiation
Absorber
The material or object that takes in the energy carried by an electromagnetic wave.
From: Types of electromagnetic waves
Absorption
The process where wave energy is taken in by a medium and converted to heat, reducing the wave's amplitude.
From: Principles of Wave Detection and Echo Sounding
Absorption rate
The amount of radiation energy an object takes in per unit of time.
From: Perfect black bodies and radiation
Acceleration
The rate of change of an object's velocity.
From: Key ideas
Acid rain
Rain made acidic by atmospheric pollution (primarily sulfur dioxide and nitrogen oxides) that causes environmental harm.
From: Environmental and Global Issues in Energy Use
Activity
The rate at which a source of unstable nuclei decays, measured in Becquerels (Bq).
From: Different half-lives of radioactive isotopes
Actual risk
The scientific, statistical probability of harm occurring based on verifiable data.
From: Uses of nuclear radiation
Aerial / Antenna
A metal conductor designed to transmit or receive radio waves.
From: Properties of electromagnetic waves 2
Airbags
A vehicle safety feature that inflates rapidly and compresses when a passenger strikes it, extending the impact time.
From: Changes in momentum
Air resistance
A resistive force acting opposite to the relative motion of an object moving through the air, sometimes called drag.
From: Resultant forces
Air resistance (drag)
A frictional force that opposes the motion of an object moving through a fluid.
From: Velocity-Time Graphs and Terminal Velocity
Albedo effect
A scale used to describe the reflectivity of a surface, where represents a perfect absorber and represents a perfect reflector.
From: Emission and absorption of infrared radiation
alpha decay
A type of radioactive decay in which an unstable nucleus emits an alpha particle (two protons and two neutrons), decreasing its mass number by 4 and its atomic number by 2.
From: Radioactive decay and nuclear radiation
Alpha particle
A type of nuclear radiation consisting of two protons and two neutrons; it has a relative mass of 4 and a charge of +2.
From: Nuclear equations
Alpha particles
Positively charged particles consisting of two protons and two neutrons (a helium nucleus) with a +2 charge.
From: The development of the model of the atom
Alpha (α) radiation
A type of nuclear radiation consisting of an alpha particle (two protons and two neutrons), carrying a +2 charge with very high ionising power but low penetrating power.
From: Radioactive decay and nuclear radiation
Alternating current (a.c.)
Current that continuously changes direction, oscillating back and forth around a circuit.
From: Direct and alternating potential difference
Alternating current (AC)
An electrical current that continuously changes direction.
From: Transformers
Alternating potential difference
A voltage that continually changes direction, induced when a coil constantly changes its direction of motion in a magnetic field.
From: Microphones
Alternator
A type of generator that uses the generator effect and slip rings to produce alternating current (AC).
From: Uses of the generator effect
Altitude
The height of an object or point in relation to sea level or ground level.
From: Atmospheric pressure
Ammeter
A device connected in series to measure the current flowing through a component, assumed to have zero resistance.
From: Series and parallel circuits
Ampere
The unit of electric current, equivalent to a rate of flow of one Coulomb per second.
From: Electrical charge and current
Amperes (A)
The standard unit of measurement for electrical current.
From: Current, resistance and potential difference
Amplitude
The maximum displacement of a wave or vibration from its undisturbed position, corresponding to the size of the current or loudness of sound in a loudspeaker.
From: Loudspeakers
Angle of incidence
The angle between the incoming (incident) ray and the normal line.
From: Reflection of waves
Angle of incidence (i)
The angle measured between the incoming incident ray and the normal.
From: Properties of electromagnetic waves 1
Angle of reflection
The angle between the outgoing (reflected) ray and the normal line.
From: Reflection of waves
Angle of refraction (r)
The angle measured between the refracted ray and the normal.
From: Properties of electromagnetic waves 1
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